Cathode active material and non-aqueous electrolyte secondary battery using the same

ABSTRACT

A cathode active material having a large capacity and improved charge/discharge cycle characteristics is disclosed. A battery has a cathode ( 2 ) having a cathode active material, an anode ( 3 ) and a non-aqueous electrolyte, and uses a cathode active material composed of a mixture of a first lithium-transition metal composite oxide containing Ni and Co and comprising a layer structure and a second lithium-transition metal composite oxide containing Ni and Mn and comprising a layer structure.

TECHNICAL FIELD

The present invention relates to a cathode active material used for abattery and also to a non-aqueous electrolyte secondary battery usingthe cathode active material.

BACKGROUND ART

In recent years, demand for secondary batteries has been rapidlyincreasing, because of advent of a large number of portable electronicappliances such as a camera-integrated VTR, a mobile phone and a laptopcomputer. With a tendency to miniaturization and lightweight of theseelectronic appliances, the secondary batteries have required a largerenergy density intended for use as portable power sources. Among thesecondary batteries, a lithium ion secondary battery is expectable invirtue of its energy density larger than that of conventional aqueouselectrolyte secondary batteries such as a lead battery and anickel-cadmium battery.

The lithium ion secondary battery practically uses, for a cathode activematerial, a lithium-cobalt composite oxide comprising a layer structure,a lithium-manganese composite oxide having a spinel structure, alithium-nickel composite oxide or the like.

(1) The lithium-manganese composite oxide having the spinel structureexhibits a stabled crystal structure, whereas there are problems that acharge capacity of the lithium-manganese composite oxide is lower thanthat of the lithium-cobalt oxide or the lithium-nickel oxide, and a hightemperature storage characteristic thereof is also somewhat inferiorthereto.(2) The lithium-nickel composite oxide is expectable in virtue ofexcellence in material cost and stabilization of supplying superior tothe lithium-cobalt composite oxide. However, there are problems that thelithium-nickel composite oxide has a crystal structure of low stability,and thereby causes lowering of charge/discharge capacity and energydensity and/or degradation of charge/discharge cycle characteristicsunder high temperature environment.

As for methods for achieving stability of the crystal structure of thelithium-nickel composite oxide to suppress lowering of charge/dischargecapacity and energy density, there are, for instance, proposals formethods such as one of upgrading cycle characteristics by substitutionof a part of nickel with a different species of element as described inJapanese Patent Laid-open Nos. Hei 5-283076 and Hei 8-37007, one ofusing a specific metal salt or the like for an additive as described inJapanese Patent Laid-open No. Hei 7-192721 and one of regulating abinder in a process of synthesis of a cathode as described in JapanesePatent Laid-open No. Hei 10-302768. However, it is still necessary forthe lithium-nickel composite oxide to have a more stabled crystalstructure to meet recent requirements for larger density of electronicappliances or the like and higher speed of integrated circuits or thelike, or environmental resistance required for mobile appliances or thelike.

There is also a proposal for a method of adding, to the lithium-nickelcomposite oxide, the spinel-type lithium-manganese composite oxide whosecrystal structure is stable. However, this method is disadvantageous inthat the spinel-type lithium-manganese composite oxide has low chargecapacity, and thereby causes lowering of charge/discharge capacity of acathode without exploiting large capacity of the lithium-nickelcomposite oxide.

(3) The lithium-cobalt composite oxide is widely used, because cost andphysical properties such as charge capacity and thermal stability arebest balanced. However, the lithium-cobalt composite oxide has problemsin cost and stabilization of supplying due to a small output of cobalt.

In the lithium-cobalt composite oxide being charged/discharged rangingfrom 4.250 V to 3.00 V to lithium metal results in a mean dischargevoltage of 3.9 V to 4.0 V or around. Thus, an over-discharge state of alithium ion battery with a cathode composed of the lithium-cobaltcomposite oxide increases a potential of an anode, and thereby causesproblems such as dissolution of copper foil used for a current collectorso as to exert a bad influence such as lowering of capacity upon thebattery when the battery was recharged. Thus, the above lithium ionbattery employs an external element such as a protection circuit toregulate a voltage in a final stage of discharge, and this constitutionhas been obstacles to miniaturization and cost reduction of the abovelithium ion battery.

The present invention is conceived in view of the above conventionalsituations, and is to provide a cathode active material having largecharge/discharge capacity and increased energy density of a cathode, andbesides, being capable of achieving excellent charge/discharge cyclecharacteristics not only at room temperature but also under hightemperature environment, and also to provide a non-aqueous electrolytebattery using the cathode active material.

In a lithium ion battery with a cathode composed of a lithium-cobaltcomposite oxide, the present invention is also to provide a cathodeactive material capable of realizing a lithium ion non-aqueouselectrolyte secondary battery, which has a large capacity and isexcellent in over-discharge resistance, and also to provide a lithiumion non-aqueous electrolyte secondary battery using the cathode activematerial.

DISCLOSURE OF THE INVENTION

A first aspect of the present invention is characterized in that acathode active material is composed of a mixture of a first cathodematerial containing at least Ni and Co and comprising a layer structureand a second cathode material containing at least Ni and Mn andcomprising a layer structure.

In the above cathode active material, the first cathode materialcontaining at least Ni and Co and comprising the layer structure and thesecond cathode material containing at least Ni and Mn and comprising thelayer structure are mixed, and the first cathode material has a largecapacity, while the second cathode material exhibits a stabled crystalstructure, resulting in achievement of larger charge/discharge capacity,improved energy density and excellent charge/discharge cyclecharacteristics-even under high temperature environment.

A non-aqueous electrolyte secondary battery of the present inventioncomprises a cathode configured so that a cathode current collector iscoated with a cathode active material compound layer containing acathode active material, an anode configured so that an anode currentcollector is coated with an anode active material compound layercontaining an anode active material, and a non-electrolyte. Thenon-aqueous electrolyte secondary battery is characterized in that thecathode active material is composed of a mixture of a first cathodematerial containing at least Ni and Co and having a layer structure anda second cathode material containing at least Ni and Mn and having alayer structure.

In the above non-aqueous electrolyte secondary battery, the cathodeactive material composed of the mixture of the first cathode materialcontaining at least Ni and Co and having the layer structure and thesecond cathode material containing at least Ni and Mn and having thelayer structure is used, and the first cathode material has a largecapacity, while the second cathode active material exhibits a stabledcrystal structure, resulting in achievement of larger charge/dischargecapacity, improved energy density and excellent charge/discharge cyclecharacteristics even under high temperature environment.

In addition, a second aspect of the present invention is characterizedin that the cathode active material used for a lithium ionnon-electrolyte secondary battery is a cathode active materialcontaining a lithium-nickel composite oxide having a layer structure andin which a shift width of 50% position (a half of the whole lithiumcontents) of jump height of nickel-K shell absorption edge obtained bymeasurement using an XAFS (X-ray Absorption Fine Structure analysis)technology is equal to or more than 1.0 eV.

The lithium ion non-aqueous electrolyte secondary battery of the presentinvention is a secondary battery comprising a cathode consisting of acathode active material composed of a material capable of inserting andextracting lithium ion, an anode consisting of an anode active materialcomposed of a material capable of inserting and extracting lithium ion,and a non-aqueous electrolyte prepared by dispersing an electrolyte in anon-aqueous medium, wherein the cathode active material is a cathodeactive material containing a lithium composite oxide in which a shiftwidth of 50% position of jump height of nickel-K shell absorption edgeobtainable by measurement using the XAFS technology is equal to or morethan 1.0 eV when 50% of the whole lithium contents was extracted.

A third aspect of the present invention is characterized in that thecathode active material is a cathode active material preferably used fora lithium ion non-aqueous electrolyte secondary battery and composed ofa first lithium-transition metal composite oxide mainly containinglithium and cobalt and having a layer structure and a secondlithium-transition metal composite oxide having a layer structure andwhose mean discharge voltage resulting from discharge down to a range of4.25 V to 3.00 V under a current of 0.2 C is lower than that of thefirst composite oxide by 0.05 V or more.

In such a cathode active material, the lithium-transition metalcomposite oxide whose mean discharge voltage is lower than that of thelithium-cobalt composite oxide by 0.05 V or more is added to thelithium-cobalt composite oxide and is used for the cathode activematerial, resulting in a cathode potential lowered in a final stage ofdischarge so as to substantially improve resistance to over-discharge.

Further, the lithium ion non-aqueous electrolyte secondary battery ofthe present invention is a secondary battery comprising a cathodeconsisting of a cathode active material composed of a material capableof inserting and extracting lithium ion, an anode consisting of an anodeactive material composed of a material capable of inserting andextracting lithium ion similarly, and a non-aqueous electrolyte havinglithium ion conductivity, wherein the cathode active material used isthe above cathode active material, specifically, the cathode activematerial composed of the first lithium-transition metal composite oxidemainly containing lithium and cobalt and the second lithium-transitionmetal composite oxide whose mean discharge voltage is lower than that ofthe first composite oxide by 0.05 V or more.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a longitudinal sectional view showing a non-aqueouselectrolyte secondary battery according to the present invention;

FIG. 2 is a sectional view showing an embodiment of a lithium ionnon-aqueous electrolyte secondary battery of the present invention;

FIG. 3 is a perspective view showing a structure of a long strip-shapedcathode;

FIG. 4 is a sectional view taken along line A-A in FIG. 2 and showing aspirally wound electrode member;

FIG. 5 is a sectional view showing another example of the spirally woundelectrode member;

FIG. 6 is a sectional view showing another example of the spirally woundelectrode member;

FIG. 7 is a sectional view showing still another example of the spirallywound electrode member;

FIG. 8 is a sectional view showing another example of the spirally woundelectrode member;

FIG. 9 is a graph showing results of XAFS measurement (Example 37) on anon-charged product and a 50%-charged product;

FIG. 10 is a graph showing results of XAFS measurement (ComparativeExample 13) on the non-charged product and the 50%-charged product;

FIG. 11 is a sectional view showing an embodiment of a lithium ionnon-aqueous electrolyte secondary battery of the present invention;

FIG. 12 is a perspective view showing a structure of a long strip-shapedcathode;

FIG. 13 is a sectional view taken along line A-A in FIG. 11 and showinga spirally wound electrode member;

FIG. 14 is a sectional view showing another example of the spirallywound electrode member;

FIG. 15 is a sectional view showing another example of the spirallywound electrode member;

FIG. 16 is a sectional view showing still another example of thespirally wound electrode member; and

FIG. 17 is a sectional view showing another example of the spirallywound electrode member.

BEST MODE FOR CARRYING OUT THE INVENTION

A cathode active material according to an embodiment of the presentinvention and a non-aqueous electrolyte secondary battery using thecathode active material will now be described in detail with referenceto the accompanying drawings.

As shown in FIG. 1, a non-aqueous electrolyte secondary battery 1 isconfigured so that an electrode member obtained by spirally winding up along strip-shaped cathode 2 and a long strip-shaped anode 3 in a closecontact manner while placing a separator 4 in between is housed in abattery container 5.

The cathode 2 is obtained by coating a cathode current collector with acathode compound material composed of a cathode active material, abinder and a conductive material in a layered form. For the binder,thermoplastic resins such as polytetrafluoroethylene, polyvinylidenefluoride and polyethylene are available. For the conductive material,artificial graphites and carbon blacks or the like are available.Specifically, the cathode current collector is composed of metal foilsuch as aluminum foil.

The cathode active material is composed of a mixture of a first cathodematerial and a second cathode material.

According to a first aspect of the present invention, the cathode activematerial is composed of a mixture of the first cathode materialcontaining at least Ni and Co and having a layer structure and thesecond cathode material containing at least Ni and Mn and having a layerstructure.

The first cathode material is a first lithium-transition metal compositeoxide having a layer structure and being expressed by a followingchemical formula (1).

Li_(x)Ni_(1-y-z)Co_(y)M_(z)O₂  (1)

where M is any one or more transition metals or elements selected fromGroup 2, 3 and 4 elements of a long form of the periodic table, and x, yand z satisfy 0.90≦x≦1.1, 0.05≦y≦0.50 and 0.01≦z≦0.10, respectively.

M in the above chemical formula (1) specifically represents an elementor elements homogeneously dispersible in grains of the firstlithium-transition metal composite oxide. More preferably, M is any oneor more elements selected from Fe, Co, Zn, Al, Sn, Cr, V, Ti, Mg and Ga.

The second cathode material is a second lithium-transition metalcomposite oxide having a layer structure and being expressed by afollowing chemical formula (2).

Li_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂  (2)

where M′ is any one or more transition metals or elements selected fromGroup 2, 3 and 4 elements of the long form of the periodic table, and s,t and u satisfy 0.90≦s≦1.1, 0.05≦t≦0.50 and 0.01≦u≦0.30, respectively.

M′ in the above chemical formula (2) specifically represents an elementor elements homogeneously dispersible in grains of the secondlithium-transition metal composite oxide. More preferably, M′ is any oneor more elements selected from Fe, Co, Zn, Al, Sn, Cr, V, Ti, Mg and Ga.

The first lithium-transition metal composite oxide and the secondlithium-transition metal composite oxide are contained preferably in amixing ratio of 15% by weight or more to 85% by weight or less, morepreferably, 30% by weight or more to 70% by weight or less to the wholecathode active material. In the cathode active material, a decrease toless than 15% by weight of the first lithium-transition metal compositeoxide in mixing ratio means an increase to more than 85% of the secondlithium-transition metal composite oxide in mixing ratio, also increasesa proportion of the low-capacity second lithium-transition metalcomposite oxide to the whole cathode active material, and thereby causeslowering of initial capacity of the cathode active material withoutexploiting a large capacity of the first lithium-transition metalcomposite oxide. On the contrary, an increase to more than 85% by weightof the first lithium-transition metal composite oxide in mixing ratiomeans a decrease to less than 15% of the second lithium-transition metalcomposite oxide in mixing ratio, also renders a crystal structure of thecathode active material unstable, and thereby promotes deterioration ofthe crystal structure under repetitive charge/discharge cycles so as tocause remarkable degradation of charge/discharge cycle capacityretention ratio under high temperature environment.

Thus, in the cathode active material, mixing in a firstlithium-transition metal composite oxide-to-second lithium-transitionmetal composite oxide ratio of 15% by weight or more to 85% by weight orless allows the first lithium-transition metal composite oxide and thesecond lithium-transition metal composite oxide to offset a change ofcharge/discharge capacity and a change of crystal structure in responseto charge/discharge, thereby minimizes the change of crystal structure,and consequently achieves improved charge/discharge cycle capacityretention ratio.

In the cathode active material, the first lithium-transition metalcomposite oxide and the second lithium-transition metal composite oxideare preferably adjusted to have a mean particle size of 30 μm or less,more preferably, from 2 μm or more to 30 μm or less. In the cathodeactive material, a decrease to less than 2 μm of the mean particle sizeof the first lithium-transition metal composite oxide and the secondlithium-transition metal composite oxide increases a contact areabetween the cathode active material and the electrolyte, and therebypromotes decomposition of an electrolyte solution so as to causedegradation of characteristics under high temperature environment. Onthe contrary, an increase to more than 30 μm of the mean particle sizeof the first lithium-transition metal composite oxide and the secondlithium-transition metal composite oxide makes it difficult tosufficiently mix the first lithium-transition metal composite oxide andthe second lithium-transition metal composite oxide, and thereby causeslowering of initial capacity and/or degradation of charge/dischargecycle capacity retention ratio under high temperature environment.

Thus, in the cathode active material, adjusting the mean particle sizeof the first lithium-transition metal composite oxide and the secondlithium-transition metal composite oxide to 30 μm or less minimizes thecontact area between the cathode active material and the electrolytesolution, also makes it possible to sufficiently mix the firstlithium-transition metal composite oxide and the secondlithium-transition metal composite oxide, and thereby achieves largerinitial capacity and improved charge/discharge cycle capacity retentionratio under high temperature environment.

In the cathode active material, Co parts in the first lithium-transitionmetal composite oxide and Mn parts in the second lithium-transitionmetal composite oxide are preferably adjusted to a range of 0.05 or moreto 0.50 or less. In the cathode active material, adjusting Co parts andMn parts to less than 0.05 renders the crystal structures of the firstlithium-transition metal composite oxide and the secondlithium-transition metal composite oxide unstable, and therebydeteriorates the crystal structure of the cathode active material underrepetitive charge/discharge cycles so as to cause degradation ofcharge/discharge cycle characteristics. On the contrary, adjusting theCo parts and Mn parts to more than 0.5 allows the cathode activematerial to form a crystal structure that brings about lowering ofcharge/discharge capacity, and thereby causes lowering ofcharge/discharge capacity.

Thus, in the cathode active material, adjusting the Co parts in thefirst lithium-transition metal composite oxide and Mn parts in thesecond lithium-transition metal composite oxide to a range of 0.05 ormore to 0.50 or less suppresses deterioration of the crystal structure,and thereby achieves improved charge/discharge cycle characteristics.Also, adjusting the Co parts and Mn parts to the range of 0.05 or moreto 0.50 or less allows the cathode active material to form alarge-capacity crystal structure, and thereby achieves largercharge/discharge capacity.

The first lithium-transition metal composite oxide and the secondlithium-transition metal composite oxide are prepared by mixingcarbonates of lithium, nickel, cobalt, manganese or the like accordingto each composition, and by sintering a mixture of carbonates in an airor oxygen atmosphere at temperatures ranging from 600° C. to 1100° C. Itis noted that a starting material is by no means limited to carbonates,and other starting materials such as hydroxides, oxides, nitrates andorganic acid-bases are also available likewise. Alternatively, compositehydroxides and/or composite carbonates containing lithium, nickel,cobalt and manganese are also available as materials for the firstlithium-transition metal composite oxide and the secondlithium-transition metal composite oxide.

The above cathode active material is composed of the mixture of thelarge-capacity first lithium-transition metal composite oxide and thesecond lithium-transition metal composite oxide having the stablecrystal structure, and thereby achieves larger charge/discharge capacityand stabilization of crystal structure. Thus, the cathode activematerial is successful in achieving larger charge/discharge capacity,larger energy density and improved charge/discharge cycle capacityretention ratio under high temperature environment. The cathode activematerial also achieves larger initial capacity and more excellentcharge/discharge cycle capacity retention ratio by regulating the mixingratio of the first lithium-transition metal composite oxide to thesecond lithium-transition metal composite oxide, the average grain sizeof the first lithium-transition metal composite oxide and the secondlithium-transition metal composite oxide, Co parts in the firstlithium-transition metal composite oxide and Mn parts in the secondlithium-transition metal composite oxide or the presence or absence ofadditive elements in the first lithium-transition metal composite oxideand the second lithium-transition metal composite oxide as describedabove.

The anode 3 is obtained by coating an anode current collector with ananode compound material composed of an anode active material and abinder. For the anode active material, materials capable of insertingand extracting lithium to electrochemically under a potential of 2.0 Vor less to lithium metal are used. Examples of available materialsinclude carbonaceous materials such as non-graphitizable carbon,artificial graphite, naturally occurred graphite, pyrolytic carbons,cokes (pitch coke, needle coke, petroleum coke and others), graphites,vitreous carbons (glass-like carbons), sintered organic polymercompounds (carbonized organic polymer compounds obtained by sinteringphenol resin, furan resin or the like at appropriate temperatures),fibrous carbon, activated carbon and carbon blacks.

Alternatively, metals capable of alloying with lithium and alloyedcompounds consisting of the metals capable of alloying with lithium arealso available as materials for the anode active material. Examples ofmetals capable of alloying with lithium include Mg, B, Al, Ga, In, Si,Sn, Pb, Sb, Bi, Cd, Ag, Zn, Hf, Zr and Y, on an assumption thatsemiconductor elements are also included. Alternatively, oxides such asruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide, tinoxide or those ensuring a relatively low potential and also insertingand extracting lithium ion and other nitrides are also availablelikewise. For the anode current collector, metal such as copper foil isused. For the conductive material, similar materials inclusive ofcarbonaceous materials such as artificial graphite and carbon black andmetals in a powdered form to those for the conductive material used infabricating the cathode 2 are used.

Fabrication of the cathode 2 and the anode 3 is carried out using anyone of methods such as one of coating mixtures prepared by adding abinder, a conductive material or the like to the cathode active materialand the anode active material and by also adding a solvent thereto, oneof coating mixtures prepared by adding a binder or the like to thecathode active material and the anode active material and by heating themixtures, and one of forming a molded electrode member by subjecting thecathode active material and the anode active material individually ormixtures thereof added with a conductive material or mixtures thereoffurther added with the binder to treatment such as molding. However,fabrication of the cathode 2 and the anode 3 is by no means limited tothe above methods.

In fabrication of the cathode 2, for instance, to the cathode activematerial prepared by mixing the first lithium-transition metal compositeoxide and the second lithium-transition metal composite oxide is addedthe above conductive material and the above binder in a predeterminedratio to prepare a cathode compound material, and the cathode compoundmaterial is further dispersed in an organic solvent such asN-methyl-2-pyrolidone to obtain a cathode compound material in a slurryform. Next, the slurry-formed cathode compound material is uniformlycoated on the cathode current collector to form a cathode activematerial compound layer, then dried and subjected to molding to therebyobtain the cathode 2.

In fabrication of the anode 3, the anode active material and the binderare mixed in a predetermined ratio to obtain an anode compound materialin a slurry form. Next, the slurry-formed anode compound material isuniformly coated on the anode current collector to form an anode activematerial compound layer, then dried and subjected to molding to therebyobtain the anode 3. In fabrication of the cathode 2 and the anode 3, itis also allowable to obtain a reinforced cathode 2 and a reinforcedanode 3 by subjecting the cathode active material and the anode activematerial with heat being applied thereto to pressure molding, no matterwhether the binder is used or not.

Manufacture of the non-aqueous electrolyte secondary battery 1 using thecathode 2 and the anode 3 is carried out using any one of methods suchas one of spirally winding up the cathode 2 and the anode 3 around acore while placing a separator 4 in between and one of stacking thecathode 2 and the anode 3 while placing the separator 4 in between.

The electrolyte may be any one of a non-aqueous electrolyte solutionprepared by dissolving an electrolyte salt in a non-aqueous solvent, asolid electrolyte containing an electrolyte salt and a gel electrolyteprepared by impregnating a non-aqueous electrolyte solution consistingof a non-aqueous solvent and an electrolyte salt into a matrix polymer.

The non-aqueous electrolyte solution is prepared by properly combiningan organic solvent and an electrolyte salt. The organic solvent may beany of those used for batteries using a non-aqueous electrolyte solutionsystem. Examples of the organic solvent include propylene carbonate,ethylene carbonate, vinylene carbonate, diethyl carbonate, dimethylcarbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone,tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane,4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane,acetonitrile, propionitrile, anisole, acetic acid ester, lactic acidester and propionic acid ester. The electrolyte salts may be any ofthose used for batteries using a non-aqueous electrolyte solutionsystem, and examples of which include LiCl, LiBr, LiClO₄, LiAsF₆, LiPF₆,LiBF₄, LiCH₃SO₃, LiCF₃SO₃, Li(CF₃SO₂)₂, LiB(C₆H₅)₄ andLiN(C_(n)F_(2n+1)SO₂)₂ or the like.

The solid electrolyte may be any of an inorganic solid electrolyte and apolymer solid electrolyte provided that these electrolytes have lithiumion conductivity. Examples of the inorganic solid electrolyte includelithium nitride and lithium iodide or the like. The polymer solidelectrolyte consists of a polymer compound containing any of theabove-described electrolyte salts. For the polymer compound, etherpolymers such as polyethylene oxide and cross-linked products thereofand ester polymers such as polymethacrylate and polyacrylate areavailable, for instance.

The matrix polymer for the gel electrolyte may be any species of organicpolymers that may be gelated after absorbing the non-aqueous electrolytesolution. Examples of the matrix polymer include fluorine-containingpolymers such as polyvinylidene fluoride and polyvinylidenefluoride-co-hexafluoro propylene, ether polymers such as polyethyleneoxide and cross-linked products thereof and poly acrylonitrile or thelike. In particular, for the matrix polymer for the gel electrolyte, itis preferable to use a fluorine-containing polymer in virtue of itsredox stability.

In particular, it is preferable to use a fluorine-containing polymermaterial so as to meet redox stability. An appropriate molecular weightof the polymer ranges from 300,000 to 800,000 or around.

Specifically, dispersion of the electrolyte into the polymer may betypically accomplished by dissolving a polymer such as polyvinylidenefluoride into a non-aqueous electrolyte solution prepared by dissolvingan electrolyte into a non-aqueous solvent so as to obtain a sol polymer.

As described above, the matrix for the gel electrolyte is given with ionconductivity by containing the electrolyte salt in the non-aqueouselectrolyte solution.

Furthermore, the solid electrolyte may be either of an inorganic solidelectrolyte and a polymer solid electrolyte provided that theseelectrolytes have lithium ion conductivity. Examples of the inorganicsolid electrolyte include crystalline solid electrolytes such as lithiumnitride and lithium iodide and amorphous solid electrolytes such aslithium ion conductive glass inclusive of LiI.Li₂S.P₂S₆ system glass andLiI.Li₂S.B₂S₆ system glass.

In addition, the polymer solid electrolyte consists of an electrolytesalt and a polymer compound that is to dissolve the electrolyte salt.For the polymer compound, ether polymers such as polyethylene oxide andcross-linked products thereof and ester polymers such aspolymethacrylate and polyacrylate are available.

While the non-aqueous electrolyte secondary battery of the presentinvention is typically configured so that the above spirally woundelectrode and the non-aqueous electrolyte are enclosed in a metal orplastic-made case or the like, it is preferable to enclose the spirallywound electrode and the non-aqueous electrolyte in a film-formedexternal case so as to meet requirements for lightweight and smallthickness. Available materials for a laminated film forming thefilm-formed external case include plastic materials such as polyethyleneterephthalate (PFT), molten polypropylene (PP), cast polypropylene(CPP), polyethylene (PE), low density polyethylene (LDPE), high densitypolyethylene (HDPE), linear chain-formed low density polyethylene(LLDPE) and polyamide-containing synthetic polymer materials (tradename: Nylon: Ny), and aluminum (Al) is used as an impermeable barrierfilm.

The most typical constitution of the laminated film may be exemplifiedby an external layer/metal layer (barrier film)/sealant layerconstitution obtained by a combination of PET/Al/PE. Alternatively, thelaminated film constitution is by no means limited to the abovecombination, and any other combinations of Ny/Al/CPP, PET/Al/CPP,PET/Al/PET/CPP, PET/Ny/Al/CPP, PET/Ny/Al/Ny/CPP, PET/Ny/Al/Ny/PE,Ny/PE/Al/LLDPE, PET/PE/Al/PET/LDPE and PET/Ny/Al/LDPE/CPP are alsoapplicable to the external layer/metal film/sealant layer constitution.It is a matter of course that any of metals other than Al is alsoavailable for the metal film.

While the lithium ion non-aqueous electrolyte secondary battery of thepresent invention comprises, as indispensable components, the cathodecontaining the cathode active material of the present invention, theanode and the non-aqueous electrolyte, a form of the battery is by nomeans limited in particular, and the battery may have a variety of formssuch as a cylinder, a square, a coin, a button, a laminated seal or thelike. In order to obtain a more secure enclosed-type non-aqueouselectrolyte secondary battery, the lithium ion non-aqueous electrolytesecondary battery further comprising a means such as a safety valve thatis operated in response to an increase of pressure inside the battery soas to interrupt a current at the time of abnormal conditions such asover-charge is preferably required.

The non-aqueous electrolyte secondary battery of the present inventionis configured with various materials described above, particularly, thespecific cathode active material, and thus provided as that having largecapacity and being excellent in over-discharge resistance.

In manufacture of a cylindrical non-aqueous electrolyte secondary batter1, firstly, thus-fabricated cathode 2 and anode 3 are spirally wound upa large number of times while placing a separator 4 made of a porouspolyolefin film in between to obtain a spirally wound electrode member.The spirally wound electrode member is enclosed, with insulator plates 6mounted on both upper and lower faces of the electrode member, in abattery container 5 made of nickel-plated iron. Current collection ofthe cathode 2 is obtained by extracting one end of a cathode lead 7 madeof aluminum from the cathode current collector, while welding the otherend to a current interrupt thin plate 8 to establish electricalconnection with a battery cap 9. Current collection of the anode 3 isobtained by extracting one end of an anode lead 10 made of nickel fromthe anode current collector, while welding the other end to a bottom ofthe battery container 5.

Next, the prepared non-aqueous electrolyte solution is poured into thebattery container 5 with the above electrode member incorporatedtherein, and thereafter, the battery cap 9 is fixed by caulking thebattery container 5 through an insulator sealing gasket 11.Specifically, the non-aqueous electrolyte secondary battery 1 has acenter pin 12 connected to the cathode lead 7 and the anode lead 10, asafety valve 13 for letting gas out of the non-aqueous electrolytesecondary battery 1 when a pressure inside the non-aqueous electrolytesecondary battery 1 increases more than a predetermined value, and a PTC(Positive Temperature Coefficient) element 14 for preventing a rise oftemperature inside the non-aqueous electrolyte secondary battery 1.

Thus-configured non-aqueous electrolyte secondary battery uses, for thecathode active material composing the cathode 2, the mixture of thelarge-capacity first lithium-transition metal composite oxide and thesecond lithium-transition metal composite oxide having the stablecrystal structure, and thereby achieves larger charge/discharge capacityand stability of crystal structure. Thus, the non-aqueous electrolytesecondary battery 1 is successful in achieving improved charge/dischargecycle capacity retention ratio at room temperature and also under hightemperature environment as well as having larger charge/dischargecapacity and larger energy density.

The present invention is also effective in being applied to manufactureof a square-shaped non-aqueous electrolyte secondary battery using awinding-up method. In this case, manufacture is carried out in such amanner that an inner diameter of a core is adjusted so as to be inconformity with a diameter of a portion having the greatest curvature inan ellipsoidal core used at the time of a winding-up process inmanufacture of the battery.

A second aspect of the present invention is characterized in that thecathode active material for the lithium ion non-electrolyte secondarybattery is a cathode active material containing a lithium-nickelcomposite oxide having a layer structure and in which a shift width of50% position (a half of the whole lithium contents) of jump height ofnickel-K shell absorption edge obtained by measurement using an XAFS(X-ray Absorption Fine Structure analysis) technology is equal to ormore than 1.0 eV.

The cathode active material of the present invention will next bedescribed in detail. It is to be noted that “%” described in thisspecification represents a mass percentage, unless otherwise specified.

As described above, the cathode active material of the present inventionis used for the lithium ion non-aqueous electrolyte secondary battery,and contains a lithium composite oxide having a layer structure andcontaining at least lithium and nickel as components.

In the above lithium composite oxide, a shift width of 50% position ofjump height of nickel-K shell absorption edge obtainable by measurementusing the X-ray absorption fine structure analysis (XAFS) technology isequal to or more than 1.0 eV when 50% of the whole lithium contents wasextracted. This obtains a cathode active material having a largecapacity and also being excellent in resistance when operated under hightemperature environment.

Preferably available materials for the lithium-transition metalcomposite oxide include materials such as LiNiO₂ or those having a layerstructure, mainly containing nickel and lithium and being capable ofallowing lithium to insert thereinto and extract therefrom.Alternatively, known materials per se prepared by substituting a part ofcomponents with a different species of element are also available.

The above constitution contributes to improvement of environmentalresistance of an oxidation state of nickel ion in the lithium-nickelcomposite oxide.

The X-ray absorption fine structure (XAFS) analysis will next bedescribed.

It is typically known that elements have the property of absorbingX-rays of specific energy due to electron transition of inner-shellelectrons. More specifically, measuring X-ray absorption spectrum on acertain element results in absorption rapidly increased when energy of acertain value or more is reached. This is called an absorption edge.What kind of form the measured element is being or a surroundingenvironment thereof is reflected by a fine structure in the vicinity ofthe absorption edge, so that analysis of an electron state or a localstructure is carried out using analysis of the fine structure.

Particularly, a structure obtained by subtracting background from theabsorption spectrum and by extending a range as much as about several 10eV in the close vicinity of jump or around of the absorption edge iscalled X-ray absorption fine structure (XAFS), by which an electronstate of a central element is mainly reflected. LiNiO₂ also shows thatthe absorption edge shifts toward a higher energy side in response tocharging (DENKI KAGAKU, 66 (1998) 968. and others, for instance).

The present invention is to regulate that the shift width of energyvalue be equal to or more than 1.0 eV between an initial state and astate obtained by extraction of 50% of lithium through charging (whichwill be hereinafter referred to as 50% charged-state), when the focus isplaced on 50% energy value of jump height of the absorption edge inXANES spectrum of Ni—K shell absorption edge of the abovelithium-transition metal composite oxide.

In the lithium-nickel oxide, it is typically known that electrons onoxygen have a great influence on charge/discharge (Journal of PowerSources, 97-98 (2001) 326. and others), and electrons on oxygen aredissipated at the time of charging.

Thus, when the lithium-nickel oxide is exposed to high temperature atthe time of charging, elimination of oxygen occurs, which thereby causesdecomposition of active materials, and in its turn, degradation ofcapacity. In other words, a decrease of electrons on nickel in place ofoxygen is preferably required to suppress degradation of capacity.

Thus, according to the present invention, the lithium composite oxidethat causes a large state change of electrons on nickel is used for thecathode active material with a change of XANES spectrum as index.

The lithium composite oxide used in the present invention alsopreferably contains either or both of manganese (Mn) and titanium (Ti).Containing these elements may further extend a range of shift width ofenergy value between the initial state and the 50% charged state.

Next, how to prepare the lithium composite oxide will be described.

The lithium-transition metal composite oxide is obtained by preparingand mixing hydroxides of Ni, Co, Mn and Ti used as transition metalsources according to each composition, by adding LiOH used as lithiumsources to a mixture of hydroxides, and by sintering the mixture in anoxygen atmosphere at temperatures ranging from 600° C. to 1100° C.

In this case, available starting materials for the transition metalsources are by no means limited to the above, and carbonates, nitratesand sulfates or the like of transition metals are also available.

Alternatively, hydroxide salts and carbonates of composite transitionmetals containing a plurality of species of transition metals are alsoavailable.

Meanwhile, for the starting materials of the lithium source, Li₂O,Li₂Co₃ and LiNiO₃ or the like may be also used in place of hydroxides.

Next, the lithium ion non-aqueous electrolyte secondary battery of thepresent invention will be described.

The non-aqueous electrolyte secondary battery comprises the cathodeconsisting of the cathode active material composed of the above lithiumcomposite oxide, the anode consisting of the anode active materialcomposed of the material capable of absorbing and releasing lithiumthereinto and therefrom, and the non-aqueous electrolyte.

Herein, an amount of nickel contained in the cathode active material ispreferably in a range of 5% to 40% in molar ratio to the total amount ofthe cathode active material. The amount of nickel within the above rangeis supposed to be effective, because a crystal structure and an electronstate that are advantageous to insertion/extraction of lithium ionthereinto and therefrom are easily yielded. The amount of nickel out ofthe above range will possibly cause large lowering of charge/dischargecapacity.

For the anode active material, materials capable of absorbing andreleasing lithium therein and therefrom (insertion/extraction)electrochemically under a potential of 2.0 V or less to lithium metalare preferably used, and there is no special limitations on shapes andspecies thereof. Examples of available materials includenon-graphitizable carbon, pyrolytic carbons, cokes (pitch coke, needlecoke and petroleum coke), graphites (naturally occurred graphite,artificial graphite and graphite), vitreous carbons (glass-likecarbons), sintered organic polymer compounds (carbonized organic polymercompounds obtained by sintering phenol resin, furan resin or the like atappropriate temperatures), fibrous carbon, activated carbon and carbonblacks or the like.

Other possible materials for the anode active material include materialsforming lithium alloys containing lithium and any one of aluminum, lead,copper, indium or the like; metal oxides such as iron oxide, rutheniumoxide, molybdenum oxide, tungsten oxide, titanium oxide, tin oxide orthose ensuring a relatively low potential and capable of absorbing andreleasing lithium thereinto and therefrom and intermetallic compounds,as well as nitrides capable of absorbing and releasing lithium thereintoand extract therefrom likewise, and polymers such as polyethylene andpolypirol capable of absorbing and releasing lithium thereinto andtherefrom.

It is to be noted that insertion of lithium into the above carbonaceousmaterials or alloyed materials may be carried out electrochemicallywithin the battery after the battery is manufactured or may be carriedout before or after manufacture of the battery as being supplied from acathode or from a lithium source other than the cathode. Alternatively,insertion of lithium may also be accomplished through material synthesisby which the anode active material is obtained as a lithium-containingmaterial at the time of manufacture of the battery.

In the lithium ion non-aqueous electrolyte secondary battery of thepresent invention, the cathode or the anode may be fabricated typicallyby forming, on the opposite faces of a long strip-shaped orrectangular-shaped current collector, a cathode active material compoundlayer or an anode active material compound layer coated with a cathodecompound material or an anode compound material containing the aboveactive material and the binder.

The current collector is by no means limited in particular, and any oneof current correctors that provide current collection functions may bealso used. From a viewpoint of forms, a current collector in a foil formor a reticular form such as meshes and expanded metal is also used inplace of the above. Available materials for the cathode currentcollector include aluminum, stainless steel and nickel or the like,while available materials for the anode current collector include copperfoil, stainless steel and nickel foil that are materials incapable ofalloying with lithium.

The cathode compound material or the anode compound material may beobtained by adding, to the above active materials, known binders such aspolyvinylidene fluoride, polyvinyl pyrolidone fluoride,styrene-butadiene resin and/or known additives inclusive of conductivematerials such as graphite if the situation permits.

The cathode active material compound layer or the anode active materialcompound layer may be obtained typically by coating the cathode compoundmaterial or the anode compound material on the opposite faces of thecurrent collector and by drying a resultant coating. Specifically, thebinder and the organic solvent or the like are mixed to obtain acompound material in a slurry form, and the slurry-formed compoundmaterial is then coated on the current collector and dried to therebyobtain the cathode active material compound layer or the anode activematerial compound layer. Alternatively, it is also allowable to obtain areinforced electrode by subjecting the active material with heat beingapplied thereto to pressure molding, no matter whether the binder isused or not.

While the lithium ion non-aqueous electrolyte secondary battery of thepresent invention comprises, as indispensable components, the cathodecontaining the cathode active material of the present invention, theanode and the non-aqueous electrolyte, a form of the battery is by nomeans limited in particular, and the battery may have a variety of formssuch as a cylinder, a square, a coin, a button or the like.

In addition, in order to obtain a more secure enclosed-type non-aqueouselectrolyte secondary battery, the lithium ion non-aqueous electrolytesecondary battery further comprising means such as a safety valve thatis operated in response to a rise of pressure inside the battery so asto interrupt a current at the time of abnormal conditions such asover-charge is preferably required.

The non-aqueous electrolyte secondary battery of the present inventionis configured with various materials described above, particularly, thespecific cathode active material, and thus provided as that having largecapacity and being excellent in capacity retention ratio in response tocharge/discharge cycles.

According to a third aspect of the present invention, the cathode activematerial is a cathode active material preferably used for the lithiumion non-aqueous electrolyte secondary battery and composed of a firstlithium-transition metal composite oxide mainly containing lithium andcobalt and having a layer structure and a second lithium-transitionmetal composite oxide having a layer structure and whose mean dischargevoltage resulting from discharge under a current of 0.2 C down to arange of 4.25 V to 3.00 V is lower than that of the first compositeoxide by 0.05 V or more.

The cathode active material of the present invention will now bedescribed in detail. It is to be noted that “%” described in thisspecification represents a mass percentage, unless otherwise specified.

As described above, the cathode active material of the present inventionis composed of a mixture of a first lithium-transition metal compositeoxide A mainly containing lithium and cobalt and having a layerstructure and a second lithium-transition metal composite oxide Bobtained as a layer compound and whose mean discharge voltage resultingfrom discharge under a current of 0.2 C down to a range of 4.25 V to3.00 V is lower than that of the above composite oxide A by 0.05 V ormore. Thus, using the mixture of these composite oxides as the cathodeactive material may obtain a non-aqueous electrolyte secondary batteryhaving large capacity and being excellent in over-discharge resistance.

The first lithium-transition metal composite oxide A used in the cathodeactive material of the present invention needs to be a material such asLiCoO₂ or those mainly containing lithium and cobalt, being capable ofinserting and extracting lithium thereinto and therefrom and having alayer structure.

It is also allowable to use any of materials obtained by substitutingpart of components such as cobalt, for instance, or about 10% thereof inmolar ratio, for instance, with a different species of elements such asAl and Mg or transition metal elements such as Ni and Mn.

It is to be noted that a description to the effect that “mainlycontaining lithium and cobalt” in this specification means that anamount of (Li+Co) contained in the composite oxide is equal to or morethan 40% in molar ratio.

The above lithium-transition metal composite oxide A is obtained byadding a lithium source such as lithium carbonate to an oxide mainlycontaining cobalt, for instance, and by sintering a mixture in an airatmosphere at temperatures ranging from 600° C. to 1100° C. Formaterials of the composite oxide A, it is also allowable to usecomposite hydroxides, composite carbonates, organic acid-bases andoxides or the like containing these elements. Synthesis is by no meanslimited to the above method, and any one of optional methods such ashydrothermal synthesis is also applicable.

Meanwhile, the second lithium-transition metal composite oxide B used inthe present invention needs to be a material including a layer compoundcapable of inserting and extracting lithium thereinto and therefrom andwhose mean discharge voltage resulting from discharge under a current of0.2 C down to a range of 4.25 V to 3.00 V is lower than that of theabove composite oxide A by 0.05 V or more.

Use of thus-added material whose mean discharge voltage is regulated tothe above value lowers a cathode potential in the final stage ofdischarge, and suppresses a rise of an anode potential so as to achieveimproved over-discharge resistance.

The materials for the second lithium-transition metal composite oxide Bare by no means limited in particular, and any one of materials whosemean discharge voltage is lower than that of the first composite oxide Aby 0.05 V or more may be used, and examples of which include compositeoxides obtained by substituting 20% or more parts of cobalt in the abovelithium-cobalt composite oxide, for instance, with transition metalelements such as Ni and Mn, more specifically, oxides expressed by achemical formula of LiCo_(x)Ni_(y)Mn_(z)O₂ (provided that “x+y+z=1”).

The above composite oxide B is obtained by adding a lithium source suchas lithium hydroxide to a composite hydroxide obtained from an inorganicsalt solution mainly containing nickel through co precipitation, forinstance, and by sintering a mixture in an air or oxygen atmosphere attemperatures ranging from 600° C. to 1100° C. For materials of thecomposite oxide B, it is also allowable to use composite carbonates,organic acid-bases and oxides or the like containing these elements.Synthesis is by no means limited to the above method, and any one ofoptional methods such as solid-phase synthesis and hydrothermalsynthesis or those that are effective in attaining the above propertiesof matter is also applicable.

Mixing of the first lithium-transition metal composite oxide A and thesecond lithium-transition metal composite oxide B may be carried outusing a known mixing method. Alternatively, a method of adhering onegrain to the other grain to thereby obtain composite grains is alsoapplicable.

As for the mixing ratio of the composite oxide A to the composite oxideB, parts of the second lithium-transition metal composite oxide B in anoxide mixture (oxide A+oxide B) are preferably in a range of 4% or moreto 50% or less. Specifically, this is because a decrease to less than 4%in parts of the composite oxide B makes it difficult to sufficientlylower the cathode potential, and thereby causes degradation ofover-discharge resistance, whereas an increase to more than 50% in partsof the composite oxide B shifts a discharge curve toward a low voltageside, and thereby becomes susceptible to lowering of battery capacity inregular use.

The second lithium-transition metal composite oxide B is preferablyadjusted to have a particle configuration, in which primary particles of5 μm or less are aggregated into secondary particles. An increase tomore than 5 μm in primary particle size causes the particles to bebroken due to expansion and shrinkage in response to charge/discharge,and thereby becomes susceptible to degradation of cycle characteristics.

The lithium-transition metal composite oxides A and B are alsopreferably adjusted to have a mean particle size of 30 μm or less, morepreferably, in a range of 2 to 3 μm. Specifically, an increase to morethan 30 μm in the mean particle size makes it difficult to sufficientlymix the composite oxides together, yields a potential distributioninside the electrode, and thereby fails to obtain intended effectssufficiently in some cases.

While the lithium ion non-aqueous electrolyte secondary battery of thepresent invention comprises, as indispensable components, the cathodecontaining the cathode active material of the present invention, theanode and the non-aqueous electrolyte, a form of the battery is by nomeans limited in particular, and the battery may have various forms suchas a cylinder, a square, a coin, a button, a laminated seal or the like.In order to obtain a more secure enclosed-type non-aqueous electrolytesecondary battery, the lithium ion non-aqueous electrolyte secondarybattery further comprising a means such as a safety valve that isoperated in response to a rise of pressure in the battery so as tointerrupt a current at the time of abnormal conditions such asover-charge is preferably required.

The non-aqueous electrolyte secondary battery of the present inventionis configured with various materials described above, particularly, thespecific cathode active material, and thus provided as that having largecapacity and being excellent in over-discharge resistance.

In the lithium ion non-aqueous electrolyte secondary battery of thepresent invention, fabrication of the cathode and the anode is carriedout, for instance, using any one of methods such as one of coating amixture prepared by adding a known binder and a known conductivematerial or the like to materials and by further adding a solvent to themixture, one of coating a mixture prepared by adding a known binder andby heating the mixture and one of forming a molded electrode member bysubjecting materials individually or a mixture thereof added with abinder or a mixture thereof further added with a conductive material totreatment such as molding. Fabrication of the cathode and the anode isby no means limited to the above methods. More specifically, thematerials are added with the binder and the organic solvent or the liketo obtain a compound material in a slurry form, and the slurry-formedcompound material is coated on the current collector and dried tothereby obtain the cathode or the anode. Alternatively, it is alsoallowable to obtain an electrode having a predetermined strength bysubjecting the active material with the heat being applied thereto topressure molding, no matter whether the binder is used or not.

Manufacture of the battery may be carried out using any one of methodssuch as one of rolling up the cathode and the anode around a core whileplacing a separator in between and one of stacking the electrodes andthe separator in order. The present invention is also effective in beingapplied to manufacture of a square-shaped battery using the winding-upmethod.

EXAMPLES

Examples and Comparative Examples of the non-aqueous electrolytesecondary battery using the cathode active material applied with thepresent invention will next be specifically described. In the followingdescription, the non-aqueous electrolyte secondary battery was assumedto be a cylindrical non-aqueous electrolyte secondary battery.

Example 1

Firstly, the first lithium-transition metal composite oxide (A) wasprepared in a following manner. For materials of the firstlithium-transition metal composite oxide, lithium hydroxide, nickelmonoxide and cobalt oxide, which are commercially available materials,were used. The lithium hydroxide, the nickel monoxide and the cobaltoxide were mixed in a following mixing ratio to prepare the firstlithium-transition metal composite oxide. Specifically, in Example 1,the first lithium-transition metal composite oxide was prepared withoutbeing added with an additive M of a compound consisting of one or moretransition metals or elements selected from Group 2, 3 and 4 elements ofthe long form of the periodic table.

Accordingly, mixing was carried out so that x, 1-y-z, y and z in theabove chemical formula (1) of Li_(x)Ni_(1-y-z)Co_(y)M_(z)O₂ expressingthe first lithium-transition metal composite oxide satisfy x=1.02,1-y-z=0.70, y=0.30 and z=0.

Next, a mixture obtained by mixing the lithium hydroxide, the nickelmonoxide and the cobalt oxide in the above mixing ratio was sintered inan oxygen atmosphere of 800° C. for 10 hours and then pulverized toobtain a first lithium-transition metal composite oxide in a powderedform. Then, analysis of thus-obtained powder was carried out using anatomic absorption spectrophotometer, and results of the analysisconfirmed that the first lithium-transition metal composite oxide isexpressed by the above chemical formula (1). In addition, measurement ofa mean particle size of the above powder was carried out using a laserdiffraction technology, and results of the measurement confirmed thatthe above powder has a mean particle size of 15 μm. Further, X-raydiffraction measurement of the above powder was carried out, and resultsof the measurement confirmed that an obtained diffraction pattern issimilar to a LiNio diffraction pattern defined in 09-0063 ofInternational Centre for Diffraction Date (which will be hereinaftersimply referred to ICDD) and also that the above powder exhibits a layerstructure similar to that of LiNiO.

Next, the second lithium-transition metal composite oxide (B) wasprepared in a following manner. For materials of the secondlithium-transition metal composite oxide, lithium hydroxide, nickelmonoxide and manganese dioxide, which are commercially availablematerials, were used. The lithium hydroxide, the nickel monoxide and themanganese dioxide were mixed in a following mixing ratio to prepare thesecond lithium-transition metal composite oxide. Specifically, thesecond lithium-transition metal composite oxide was prepared withoutbeing added with an additive M′ of a compound consisting of one or moretransition metals or elements selected from Group 2, 3 and 4 elements ofthe long form of the periodic table of elements, like the firstlithium-transition metal composite oxide. Thus-prepared second lithiumtransition metal oxide is a second lithium-transition metal compositeoxide expressed by a following chemical formula (2).

Mixing was carried out so that s, 1-t-u, t and u in the chemical formula(2) of Li_(s)N_(1-t-u)Mn_(t)M′_(u)O₂ expressing the secondlithium-transition metal composite oxide satisfy s=1.02, 1-t-u=0.65,t=0.35 and u=0.

Next, a mixture obtained by mixing the lithium hydroxide, the nickelmonoxide and the manganese dioxide in the above mixing ratio wassintered in an oxygen atmosphere of 800° C. for 10 hours, and thenpulverized to obtain a second lithium-transition metal composite oxidein a powdered form. Analysis of thus-obtained powder was carried outusing an atomic absorption spectrophotometer, and results of theanalysis confirmed that the second lithium-transition metal compositeoxide is expressed by the above chemical formula (2). In addition,measurement of a mean particle size of the above powder was carried outusing a laser diffraction technology, and results of measurementconfirmed that the above powder has a means particle size of 15 μm.Further, X-ray diffraction measurement of the above powder was carriedout, and results of the measurement confirmed that an obtaineddiffraction pattern is similar to a LiNio diffraction pattern defined in09-0063 of ICDD and also that the above powder exhibits a layerstructure similar to that of LiNiO.

Next, a cathode was fabricated. First, the lithium-transition metalcomposite oxide and the second lithium-transition metal composite oxidewere mixed to prepare a cathode active material. The cathode activematerial was obtained by mixing in a first lithium-transition metalcomposite oxide-to-second lithium-transition metal composite oxide ratioof 50% by weight to 50% by weight. Next, 86% by weight of the cathodeactive material obtained by mixing the first lithium-transition metalcomposite oxide and the second lithium-transition metal composite oxide,10% by weight of graphite as a conductive material and 4% by weight ofpolyvinylidene fluoride (which will be hereinafter referred to PVdF) asa binder were mixed and further added with N-methyl-2-pyrolidone (whichwill be hereinafter referred to as NMP) as an organic solvent to obtaina cathode compound material in a slurry form. Next, the slurry-formedcathode compound material was coated uniformly on the opposite faces ofa long strip-shaped aluminum foil of 20 μm thick to form a cathodeactive material compound layer, then dried and compressed using a rollpress machine to thereby obtain a cathode in a form of a long strip.

Next, an anode was fabricated. Artificial graphite in a powdered formwas used for an anode active material, and to 90% by weight ofartificial graphite was added 10% by weight of PVdF and further addedwith NMP to obtain an anode compound material in a slurry form. Theslurry-formed anode compound material was uniformly coated on theopposite faces of a copper foil of 10 μm thick to form an anode activematerial compound layer, then dried and compressed using a roll pressmachine to thereby obtain an anode.

Next, a non-aqueous electrolyte solution was prepared. The non-aqueouselectrolyte solution was obtained by dissolving LiPF₆ as solute in asolution prepared by mixing ethylene carbonate and methyl ethylcarbonate in a volume mixing ratio of 1:1 so as to adjust theconcentration thereof to 1.0 mol/dm.

Next, a cylindrical non-aqueous electrolyte secondary battery wasmanufactured. First, thus-fabricated cathode and anode were spirallywound up a large number of times while placing a separator made of aporous polyolefin film in between to manufacture a spirally woundelectrode member. The spirally wound electrode member is enclosed, withinsulator plates mounted to both upper and lower faces of the electrodemember, in a battery container made of nickel-plated iron. Currentcollection of the cathode was obtained by extracting one end of acathode lead made of aluminum from the cathode current collector, whilewelding the other end to a current interrupt thin plate to establishelectrical connection to a battery cap through the current interruptthin plate. Current collection of the anode was obtained by extractingone end of the anode lead made of nickel from the anode currentcollector, while welding the other end to a bottom of the batterycontainer.

Next, thus-prepared non-aqueous electrolyte solution was poured into thebattery container with the above electrode member incorporated therein,and thereafter, the battery cap was fixed by caulking the batterycontainer through an insulator sealing gasket to thereby fabricate acylindrical non-aqueous electrolyte secondary battery having a diameterof 18 mm and a height of 65 mm. Specifically, the non-aqueouselectrolyte secondary battery has a center pin connected to the cathodelead and the anode lead, a safety valve for letting gas out of thenon-aqueous electrolyte battery when a pressure inside the non-aqueouselectrolyte secondary battery increases more than a predetermined value,and a PTC (Positive Temperature Coefficient) element for preventing arise of temperature in the non-aqueous electrolyte secondary battery.

Example 2

In Example 2, aluminum hydroxide was used, in addition to the lithiumhydroxide, the nickel monoxide and the cobalt oxide, for the materialsof the first lithium-transition metal composite oxide, and thesematerials were mixed in a following ratio. The first lithium-transitionmetal composite oxide of LiNiCOAlO was prepared similarly to Example 1,except that mixing was carried out so that x, 1-y-z, y, z and M in thechemical formula (1) of Li_(x)Ni_(1-y-z)Co_(y)M_(z)O₂ expressing thefirst lithium-transition metal composite oxide satisfy x=1.02,1-y-z=0.70, y=0.25, z=0.05 and M=Al. Except for using this firstlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 1.

Example 3

In Example 3, aluminum hydroxide was used, in addition to the lithiumhydroxide, the nickel monoxide and the cobalt oxide, for materials ofthe second lithium-transition metal composite oxide, and these materialswere mixed in a following ratio. The second lithium-transition metalcomposite oxide of LiNiMnAlO was prepared similarly to Example 1, exceptthat mixing was carried out so that s, 1-t-u, t, u and M′ in thechemical formula (2) of Li_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂ expressing thesecond lithium-transition metal composite oxide satisfy s=1.02,1-t-u=0.65, t=0.30, u=0.05 and M′=Al. Except for using this secondlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 1.

Example 4

In Example 4, the first lithium-transition metal composite oxideexpressed by the chemical formula of LiNiCoAlO was prepared as the firstlithium-transition metal composite oxide similarly to the firstlithium-transition metal composite oxide in Example 2. The secondlithium-transition metal composite oxide expressed by the chemicalformula LiNiMnAlO was prepared as the second lithium-transition metalcomposite oxide similarly to the second lithium-transition metalcomposite oxide in Example 3. Except for using this firstlithium-transition metal composite oxide and this secondlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 1.

Example 5

In Example 5, a first lithium-transition metal composite oxide ofLiNiCoFeO was prepared similarly to Example 4, except that ironhydroxide in place of the aluminum hydroxide was used, in addition tothe lithium hydroxide, the nickel monoxide and the cobalt oxide, formaterials of the first lithium-transition metal composite oxide, andmixing was carried out so that x, 1-y-z, y, z and M in the chemicalformula (1) of Li_(x)Ni_(1-y-z)Co_(y)M_(z)O₂ expressing the firstlithium-transition metal composite oxide satisfy x=1.02, 1-y-z=0.70,y=0.25, z=0.05 and M=Fe. Except for using this first lithium-transitionmetal composite oxide, the non-aqueous electrolyte secondary battery wasmanufactured similarly to Example 4.

Example 6

In Example 6, a first lithium-transition metal composite oxide ofLiNiCoSnO was prepared similarly to Example 4, except that tin oxide inplace of the aluminum hydroxide was used, in addition to the lithiumhydroxide, the nickel monoxide and the cobalt oxide, for materials ofthe first lithium-transition metal composite oxide, and mixing wascarried out so that x, 1-y-z, y, z and M in the chemical formula (1) ofLi_(x)Ni_(1-y-z)Co_(y)M_(z)O₂ expressing the first lithium-transitionmetal composite oxide satisfy x=1.02, 1-y-z=0.70, y=0.25, z=0.05 andM=Sn. Except for using this first lithium-transition metal compositeoxide, the non-aqueous electrolyte secondary battery was manufacturedsimilarly to Example 4.

Example 7

In Example 7, a first lithium-transition metal composite oxide ofLiNiCoCrO was prepared similarly to Example 4, except that chromiumoxide in place of the aluminum hydroxide was used, in addition to thelithium hydroxide, the nickel monoxide and the cobalt oxide, formaterials of the first lithium-transition metal composite oxide, andmixing was carried out so that x, 1-y-z, y, z and M in the chemicalformula (1) of Li_(x)Ni_(1-y-z)Co_(y)M_(z)O₂ expressing the firstlithium-transition metal composite oxide satisfy x=1.02, 1-y-z=0.70,y=0.25, z=0.05 and M=Cr. Except for using this first lithium-transitionmetal composite oxide, the non-aqueous electrolyte secondary battery wasmanufactured similarly to Example 4.

Example 8

In Example 8, a first lithium-transition metal composition oxide ofLiNiCoVO was prepared similarly to Example 4, except that vanadiumpentoxide in place of the aluminum hydroxide was used, in addition tothe lithium hydroxide, the nickel monoxide and the cobalt oxide, formaterials of the first lithium-transition metal composite oxide, andmixing was carried out so that x, 1-y-z, y, z and M in the chemicalformula (1) of Li_(x)Ni_(1-y-z)Co_(y)M_(z)O₂ expressing the firstlithium-transition metal composite oxide satisfy x=1.02, 1-y-z=0.70,y=0.25, z=0.05 and M=V. Except for using this first lithium-transitionmetal composite oxide, the non-aqueous electrolyte secondary battery wasmanufactured similarly to Example 4.

Example 9

In Example 9, a first lithium-transition metal composite oxide ofLiNiCoTiO was prepared similarly to Example 4, except that titaniumoxide in place of the aluminum hydroxide was used, in addition to thelithium hydroxide, the nickel monoxide and the cobalt oxide, formaterials of the first lithium-transition metal composite oxide, andmixing was carried out so that x, 1-y-z, y, z and M in the chemicalformula (1) of Li_(x)Ni_(1-y-z)Co_(y)M_(z)O₂ expressing the firstlithium-transition metal composite oxide satisfy x=1.02, 1-y-z=0.70,y=0.25, z=0.05 and M=Ti. Except for using this first lithium-transitionmetal composite oxide, the non-aqueous electrolyte secondary battery wasmanufactured similarly to Example 4.

Example 10

In Example 10, a first lithium-transition metal composite oxide ofLiNiCoMgO was prepared similarly to Example 4, except that magnesiumoxide in place of the aluminum hydroxide was used, in addition to thelithium hydroxide, the nickel monoxide and the cobalt oxide, formaterials of the first lithium-transition metal composite oxide, andmixing was carried out so that x, 1-y-z, y, z and M in the chemicalformula (1) of Li_(x)Ni_(1-y-z)Co_(y)M_(z)O₂ expressing the firstlithium-transition metal composite oxide satisfy x=1.02, 1-y-z=0.70,y=0.25, Z=0.05 and M=Mg. Except for using this first lithium-transitionmetal composite oxide, the non-aqueous electrolyte secondary battery wasmanufactured similarly to Example 4.

Example 11

In Example 11, a first lithium-transition metal composite oxide ofLiNiCoGaO was prepared similarly to Example 4, except that galliumnitrate in place of the aluminum hydroxide was used, in addition to thelithium hydroxide, the nickel monoxide and the cobalt oxide, formaterials of the first lithium-transition metal composite oxide, andmixing was carried out so that x, 1-y-z, y, z and M in the chemicalformula (1) of Li_(x)Ni_(1-y-z)Co_(y)M_(z)O₂ expressing the firstlithium-transition metal composite oxide satisfy x=1.02, 1-y-z=0.70,y=0.25, z=0.05 and M=Ga. Except for using this first lithium-transitionmetal composite oxide, the non-aqueous electrolyte secondary battery wasmanufactured similarly to Example 4.

Example 12

In Example 12, a second lithium-transition metal composite oxide ofLiNiMnFeO was prepared similarly to Example 4, except that ironhydroxide in place of the aluminum hydroxide was used, in addition tothe lithium hydroxide, the nickel monoxide and the cobalt oxide, formaterials of the second lithium-transition metal composite oxide, andmixing was carried out so that s, 1-t-u, t, u and M′ in the chemicalformula (2) of Li_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂ expressing the secondlithium-transition metal composite oxide satisfy s=1.02, 1-t-u=0.65,t=0.30, u=0.05 and M′=Fe. Except for using this first lithium-transitionmetal composite oxide, the non-aqueous electrolyte secondary battery wasmanufactured similarly to Example 4.

Example 13

In Example 13, a second lithium-transition metal composite oxide ofLiNiMnCoO was prepared similarly to Example 4, except that cobalt oxidein place of the aluminum hydroxide was used, in addition to the lithiumhydroxide, the nickel monoxide and the cobalt oxide, for materials ofthe second lithium-transition metal composite oxide, and mixing wascarried out so that s, 1-t-u, t, u and M′ in the chemical formula (2) ofLi_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂ expressing the second lithium-transitionmetal composite oxide satisfy s=1.02, 1-t-u=0.65, t=0.30, u=0.05 andM′=Co. Except for using this second lithium-transition metal compositeoxide, the non-aqueous electrolyte secondary battery was manufacturedsimilarly to Example 4.

Example 14

In Example 14, a second lithium-transition metal composite oxide ofLiNiMnZnO was prepared similarly to Example 4, except that zinchydroxide in place of the aluminum hydroxide was used, in addition tothe lithium hydroxide, the nickel monoxide and the cobalt oxide, formaterials of the second lithium-transition metal composite oxide, andmixing was carried out so that s, 1-t-u, t, u and M′ in the chemicalformula (2) of Li_(s)Ni_(1-t-u)Mn_(t)M′O₂ expressing the secondlithium-transition metal composite oxide satisfy s=1.02, 1-t-u=0.65,t=0.30, u=0.05 and M′=Zn. Except for using this secondlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Example 15

In Example 15, a second lithium-transition metal composite oxide ofLiNiMnSnO was prepared similarly to Example 4, except that tin oxide inplace of the aluminum hydroxide was used, in addition to the lithiumhydroxide, the nickel monoxide and the cobalt oxide, for materials ofthe second lithium-transition metal composite oxide, and mixing wascarried out so that s, 1-t-u, t, u and M in the chemical formula (2) ofLi_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂ expressing the second lithium-transitionmetal composite oxide satisfy s=1.02, 1-t-u=0.65, t=0.30, u=0.05 andM=Sn. Except for using this second lithium-transition metal compositeoxide, the non-aqueous electrolyte secondary battery was manufacturedsimilarly to Example 4.

Example 16

In Example 16, a second lithium-transition metal composite oxide ofLiNiMnCrO was prepared similarly to Example 1, except that chromiumoxide in place of the aluminum hydroxide was used, in addition to thelithium hydroxide, the nickel monoxide and the cobalt oxide, formaterials of the second lithium-transition metal composite oxide, andmixing was carried out so that s, 1-t-u, t, u and M′ in the chemicalformula (2) of Li_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂ expressing the secondlithium-transition metal composite oxide satisfy s=1.02. 1-t-u=0.65,t=0.30, u=0.05 and M′=Cr. Except for using this secondlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Example 17

In Example 17, a second lithium-transition metal composite oxide ofLiNiMnVO was prepared similarly to Example 4, except that vanadiumpentoxide in place of the aluminum hydroxide was used, in addition tothe lithium hydroxide, the nickel monoxide and the cobalt oxide, formaterials of the second lithium-transition metal composite oxide, andmixing was carried out so that s, 1-t-u, t, u and M′ in the chemicalformula (2) of Li_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂ expressing the secondlithium-transition metal composite oxide satisfy s=1.02, 1-t-u=0.65,t=0.30, u=0.05 and M′=V. Except for using this second lithium-transitionmetal composite oxide, the non-aqueous electrolyte secondary battery wasmanufactured similarly to Example 4.

Example 18

In Example 18, a second lithium-transition metal composite oxide ofLiNiMnTiO was prepared similarly to Example 4, except that titaniumoxide in place of the aluminum hydroxide was used, in addition to thelithium hydroxide, the nickel monoxide and the cobalt oxide, formaterials of the second lithium-transition metal composite oxide, andmixing was carried out so that s, 1-t-u, t, u and M′ in the chemicalformula (2) of Li_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂ expressing the secondlithium-transition metal composite oxide satisfy s=1.02, 1-t-u=0.65,t=0.30, t=0.05 and M′=Ti. Except for using this secondlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Example 19

In Example 19, a second lithium-transition metal composite oxide ofLiNiMnMgO was prepared similarly to Example 4, except that magnesiumoxide in place of the aluminum hydroxide was used, in addition to thelithium hydroxide, the nickel monoxide and the cobalt oxide, formaterials of the second lithium-transition metal composite oxide, andmixing was carried out so that s, 1-t-u, t, u and M′ in the chemicalformula (2) of Li_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂ expressing the secondlithium-transition metal composite oxide satisfy s=1.02, 1-t-u=0.65,t=0.30, u=0.05 and M′=Mg. Except for using this secondlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Example 20

In Example 20, a second lithium-transition metal composite oxide ofLiNiMnGaO was prepared similarly to Example 4, except that galliumnitrate in place of the aluminum hydroxide was used, in addition to thelithium hydroxide, the nickel monoxide and the cobalt oxide, formaterials of the second lithium-transition metal composite oxide, andmixing was carried out so that s, 1-t-u, t, u and M′ in the chemicalformula (2) of Li_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂ expressing the secondlithium-transition metal composite oxide satisfy s=1.02, 1-t-u=0.65,t=0.30, u=0.05 and M′=Ga. Except for using this secondlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Example 21

In Example 21, a cathode active material was prepared similarly toExample 4, except that mixing was carried out in a firstlithium-transition metal composite oxide (A)-to-secondlithium-transition metal composite oxide (B) ratio of 15% by weight to85% by weight. Except for using this cathode active material, thenon-aqueous electrolyte secondary battery was manufactured similarly toExample 4.

Example 22

In Example 22, a cathode active material was prepared similarly toExample 4, except that mixing was carried out in a firstlithium-transition metal composite oxide (A)-to-secondlithium-transition metal composite oxide (B) ratio of 30% by weight to70% by weight. Except for using this cathode active material, thenon-aqueous electrolyte secondary battery was manufactured similarly toExample 4.

Example 23

In Example 23, a cathode active material was prepared similarly toExample 4, except that mixing was carried out in a firstlithium-transition metal composite oxide (A)-to-secondlithium-transition metal composite oxide (B) ratio of 70% by weight to30% by weight. Except for using this cathode active material, thenon-aqueous electrolyte secondary battery was manufactured similarly toExample 4.

Example 24

In Example 24, a cathode active material was prepared similarly toExample 4, except that mixing was carried out in a firstlithium-transition metal composite oxide (A)-to-secondlithium-transition metal composite oxide (B) ratio of 85% by weight to15% by weight. Except for using this cathode active material, thenon-aqueous electrolyte secondary battery was manufactured similarly toExample 4.

Example 25

A first lithium-transition metal composite oxide having a mean particlesize of 2 μm was prepared by pulverizing the first lithium-transitionmetal composite oxide of the chemical formula of LiNiCOAlO, which wasobtained by sintering through operations similarly to Example 4, usingan automatic mortar for a sufficient period of time, and by removingcoarse particles therefrom using a sieve. Except for using this firstlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Example 26

A first lithium-transition metal compound oxide having a mean particlesize of 8 μm was prepared by pulverizing the first lithium-transitionmetal composite oxide of the chemical formula of LiNiCoAlO, which wasobtained by sintering through operations similarly to Example 4, usingan automatic mortar for a certain period of time, and by removing coarseparticles therefrom using a sieve. Except for using this firstlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Example 27

A first lithium-transition metal compound oxide having a mean particlesize of 20 μm was prepared by pulverizing the first lithium-transitionmetal composite oxide of the chemical formula of LiNiCoAlO, which wasobtained by sintering through operations similarly to Example 4, usingan automatic mortar for a short period of time, and by removing coarseparticles therefrom using a sieve. Except for using this firstlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Example 28

A first lithium-transition metal composite oxide having a mean particlesize of 30 μm was prepared by pulverizing the first lithium-transitionmetal composite oxide of the chemical formula of LiNiCoAlO, which wasobtained by sintering through operations similarly to Example 4, usingan automatic mortar for a short period of time, and by removing coarseparticles therefrom using a sieve. Except for using this firstlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Example 29

A second lithium-transition metal composite oxide having a mean particlesize of 2 μm was prepared by pulverizing the second lithium-transitionmetal composite oxide of the chemical formula of LiNiMnAlO, which wasobtained by sintering through operations similarly to Example 4, usingan automatic mortar for a sufficient period of time, and by removingcoarse particles therefrom using a sieve. Except for using this secondlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Example 30

A second lithium-transition metal composite oxide having a mean particlesize of 9 μm was prepared by pulverizing the second lithium-transitionmetal composite oxide of the chemical formula of LiNiMnAlO, which wasobtained by sintering through operations similarly to Example 4, usingan automatic mortar for a sufficient period of time, and by removingcoarse particles therefrom using a sieve. Except for using thissecond-lithium transition metal composite oxide, the non-aqueouselectrolyte secondary battery was manufactured similarly to Example 4.

Example 31

A second lithium-transition metal composite oxide having a mean particlesize of 18 μm was prepared by pulverizing the second lithium-transitionmetal composite oxide of the chemical formula of LiNiMnAlO, which wasobtained by sintering through operations similarly to Example 4, usingan automatic mortar for a certain period of time, and by removing coarseparticles therefrom using a sieve. Except for using this secondlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Example 32

A second lithium-transition metal composite oxide having a mean particlesize of 30 μm was prepared by pulverizing the second lithium-transitionmetal composite oxide of the chemical formula of LiNiMnAlO, which wasobtained by sintering through operations similarly to Example 4, usingan automatic mortar for a short period of time, and by removing coarseparticles therefrom using a sieve. Except for using this secondlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Example 33

In Example 33, cobalt parts y in the first lithium-transition metalcomposite oxide were altered to 0.05, more specifically, the firstlithium-transition composite oxide was prepared under conditions thatmixing was carried out so that x, 1-y-z, y, z and M in the chemicalformula (1) of Li_(x)Ni_(1-y-z)Co_(y)M_(z)O₂ expressing the firstlithium-transition metal composite oxide satisfy x=1.02, 1-y-z=0.90,y=0.05, z=0.05 and M=Al. Except for using this first lithium-transitionmetal composite oxide, the non-aqueous electrolyte secondary battery wasmanufactured similarly to Example 4.

Example 34

In Example 34, cobalt parts y in the first lithium-transition metalcomposite oxide were altered to 0.50, more specifically, the firstlithium-transition metal composite oxide was prepared similarly to thefirst lithium-transition metal composite oxide in Example 4 underconditions that mixing was carried out so that x, 1-y-z, y, z and M inthe chemical formula (1) of Li_(x)Ni_(1-y-z)Co_(y)M_(z)O₂ expressing thefirst lithium-transition metal composite oxide satisfy x=1.02,1-y-z=0.45, y=0.5, z=0.05 and M=Al. Except for using this firstlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Example 35

In Example 35, manganese parts t in the second lithium-transition metalcomposite oxide were altered to 0.05, more specifically, the secondlithium-transition metal composite oxide was prepared similarly to thesecond lithium-transition metal composite oxide in Example 4 underconditions that mixing was carried out so that s, 1-t-u, t, u and M′ inthe chemical formula (2) of Li_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂ expressingthe second lithium-transition metal composite oxide satisfy s=1.02,1-t-u=0.90, t=0.05, u=0.05 and M′=Al. Except for using this secondlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Example 36

In Example 36, manganese parts t in the second lithium-transition metalcomposite oxide were altered to 0.50, more specifically, the secondlithium-transition metal composite oxide was prepared similarly to thesecond lithium-transition metal composite oxide in Example 4 underconditions that mixing was carried out so that s, 1-t-u, t, u and M′ inthe chemical formula (2) of Li_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂ expressingthe second lithium-transition metal composite oxide satisfy s=1.02,1-t-u=0.45, t=0.5, u=0.05 and M′=Al. Except for using this secondlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Comparative Example 1

In Comparative Example 1, lithium hydroxide, nickel monoxide and cobaltoxide were used for materials of a first lithium-transition metalcomposite oxide and mixed in a following mixing ratio. Mixing wascarried out so that x, 1-y-z, y, z in the chemical formula (1) ofLi_(x)Ni_(1-y-z)Co_(y)M_(z)O₂ expressing the first lithium-transitionmetal composite oxide satisfy x=1.02, 1-y-z=0.70, y=0.30 and z=0. Thefirst lithium-transition metal composite oxide is expressed by thechemical formula of LiNiCoO and was prepared similarly to the firstlithium-transition metal composite oxide in Example 4. In ComparativeExample 1, a cathode active material singly composed of the firstlithium-transition metal composite oxide was prepared without using thesecond lithium-transition metal composite oxide. Except for using thiscathode active material, the non-aqueous electrolyte secondary batterywas manufactured similarly to Example 4.

Comparative Example 2

In Comparative Example 2, lithium hydroxide, nickel monoxide andmanganese dioxide, which are commercially available materials, were usedfor materials of a second lithium-transition metal composite oxide. Asthe second lithium-transition metal composite oxide expressed by achemical formula of LiNiMnO, a second lithium-transition metal compositeoxide of Li_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂ was prepared similarly toExample 4. In Comparative Example 2, a cathode active material singlycomposed of the second lithium-transition metal composite oxide wasprepared without using the first lithium-transition metal compositeoxide. Except for using this cathode active material, the non-aqueouselectrolyte secondary battery was manufactured similarly to Example 4.

Comparative Example 3

In Comparative Example 3, a cathode active material was preparedsimilarly to Example 4, except that mixing was carried out in a firstlithium-transition metal composite oxide-to-second lithium-transitionmetal composite oxide ratio of 10% by weight to 90% by weight. Exceptfor using this cathode active material, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Comparative Example 4

In Comparative Example 4, a cathode active material was preparedsimilarly to Example 4, except that mixing was carried out in a firstlithium-transition metal composite oxide-to-second lithium-transitionmetal composite oxide ratio of 90% by weight to 10% by weight. Exceptfor using this cathode active material, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Comparative Example 5

A first lithium-transition metal composite oxide having a mean particlesize of 1 μm was prepared by pulverizing the first lithium-transitionmetal composite oxide of the chemical formula of LiNiCoAlO, which wasobtained by sintering through operations similarly to Example 4, usingan automatic mortar for a sufficient period of time, and by removingcoarse particles therefrom using a sieve. Except for using this firstlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Comparative Example 6

A first lithium-transition metal composite oxide having a mean particlesize of 40 μm was prepared by pulverizing the first lithium-transitionmetal composite oxide of the chemical formula of LiNiCoAlO, which wasobtained by sintering through operations similarly to Example 4, usingan automatic mortar for a short period of time, and by removing coarseparticles therefrom using a sieve. Except for using this firstlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Comparative Example 7

A second lithium-transition metal composite oxide having a mean particlesize of 1 μm was prepared by pulverizing the second lithium-transitionmetal composite oxide of the chemical formula of LiNiMnAlO, which wasobtained by sintering through operations similarly to Example 4, usingan automatic mortar for a sufficient period of time, and by removingcoarse particles therefrom using a sieve. Except for using this secondlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Comparative Example 8

A second lithium-transition metal composite oxide having a mean particlesize of 40 μm was prepared by pulverizing the second lithium-transitionmetal composite oxide of the chemical formula of LiNiMnAlO, which wasobtained by sintering through operations similarly to Example 4, usingan automatic mortar for a sufficient period of time, and by removingcoarse particles therefrom using a sieve. Except for using thissecond-lithium transition metal composite oxide, the non-aqueouselectrolyte secondary battery was manufactured similarly to Example 4.

Comparative Example 9

In Comparative Example 9, cobalt parts y in the first lithium-transitionmetal composite oxide was altered to 0.01, more specifically, the firstlithium-transition metal composite oxide was prepared similarly to thefirst lithium-transition metal composite oxide in Example 4 underconditions that mixing was carried out so that x, 1-y-z, y, z and M inthe chemical formula (1) of Li_(x)Ni_(1-y-z)Co_(y)M_(z)O₂ expressing thefirst lithium-transition metal composite oxide satisfy x=1.02,1-y-z=0.70, y=0.01, z=0.05 and M=Al. Except for using this firstlithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 4.

Comparative Example 10

In Comparative Example 10, cobalt parts y in the firstlithium-transition metal composite oxide were altered to 0.60, morespecifically, the first lithium-transition metal composite oxide wasprepared similarly to the first lithium-transition metal composite oxidein Example 4 under conditions that mixing was carried out so that x,1-y-z, y, z and M in the chemical formula (1) ofLi_(x)Ni_(1-y-z)Co_(y)M_(z)O₂ expressing the first lithium-transitionmetal composite oxide satisfy x=1.02, 1-y-z=0.70, y=0.60, z=0.05 andM=Al. Except for using this first lithium-transition metal compositeoxide, the non-aqueous electrolyte secondary battery was manufacturedsimilarly to Example 4.

Comparative Example 11

In Comparative Example 11, manganese parts t in the secondlithium-transition metal composite oxide were altered to 0.01, morespecifically, the second lithium-transition metal composite oxide wasprepared similarly to the second lithium-transition metal compositeoxide in Example 4 under conditions that mixing was carried out so thats, 1-t-u, t, u and M′ in the chemical formula (2) ofLi_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂ expressing the second lithium-transitionmetal composite oxide satisfy s=1.02, 1-t-u=0.70, t=0.01, u=0.05 andM′=Al. Except for using this second lithium-transition metal compositeoxide, the non-aqueous electrolyte secondary battery was manufacturedsimilarly to Example 4.

Comparative Example 12

In Comparative Example 12, manganese parts t in the secondlithium-transition metal composite oxide was altered to 0.60, morespecifically, the second lithium-transition metal composite oxide wasprepared similarly to the second lithium-transition metal compositeoxide in Example 4 under conditions that mixing was carried out so thats, 1-t-u, t, u and M′ in the chemical formula (2) ofLi_(s)Ni_(1-t-u)Mn_(t)M′_(u)O₂ expressing the second lithium-transitionmetal composite oxide satisfy s=1.02, 1-t-u=0.70, t 0.60, u=0.05 andM′=Al. Except for using this second lithium-transition metal compositeoxide, the non-aqueous electrolyte secondary battery was manufacturedsimilarly to Example 4.

Next, thus-fabricated non-aqueous electrolyte secondary batteries inExamples and Comparative Examples were subjected to measurements ofinitial discharge capacity under conditions that the batteries werecharged under a current of 1000 mA and a voltage of 4.20 V in anatmosphere of 23° C. for 2.5 hours and then discharged under a currentof 1500 mA down to 2.75 V. Measurement of relative discharge capacityafter the 100th cycle in an atmosphere of 23° C. was also carried out byrepeating charge/discharge under conditions similar to those for themeasurement of the initial discharge capacity, so as to calculatecapacity retention ratio after the 100th cycle to the initial dischargecapacity. Measurement of capacity retention ratio after the 100th cycleunder repetitive charge/discharge in an atmosphere of 50° C. was alsocarried out under conditions similar to those for the measurement in theatmosphere of 23° C., except that a temperature was set at 50° C.

Table 1 shows evaluation results of the initial discharge capacity, thecapacity retention ratio after the 100th cycle in the atmosphere of 23°C. and the capacity retention ratio after the 100th cycle in theatmosphere of 50° C. in Examples 1 to 20 and Comparative Examples 1 and2.

TABLE 1 M in first M′ in second lithium- lithium- transition transitionMixing ratio Composition of first Composition of second Initial Capacityretention metal metal (A)/(B) lithium-transition lithium-transitiondischarge ratio after 100th composite composite (% by metal compositeoxide metal composite oxide capacity cycle [%] oxide (A) oxide (B)weight) (A) (B) [mAh] 23° C. 50° C. Example 1 None None 50/50Li_(1.02)Ni_(0.70)Co_(0.30)O₂ Li_(1.02)Ni_(0.65)Mn_(0.35)O₂ 1720 91.381.9 2 Al NZ 50/50 Li_(1.02)Ni_(0.70)Co_(0.25)Al_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.35)O₂ 1710 93.1 82.9 3 None Al 50/50Li_(1.02)Ni_(0.70)Co_(0.30)O₂ Li_(1.02)Ni_(0.65)Mn_(0.30)Al_(0.05)O₂1690 93.4 83.1 4 Al Al 50/50 Li_(1.02)Ni_(0.70)Co_(0.25)Al_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Al_(0.05)O₂ 1700 95.2 84.5 5 Fe Al 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Fe_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Al_(0.05)O₂ 1690 94.4 84.4 6 Sn Al 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Sn_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Al_(0.05)O₂ 1710 94.8 83.8 7 Cr Al 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Cr_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Al_(0.05)O₂ 1710 95 84.6 8 V Al 50/50Li_(1.02)Ni_(0.70)Co_(0.25)V_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Al_(0.05)O₂ 1720 93.9 84.3 9 Ti Al 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Ti_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Al_(0.05)O₂ 1680 94.9 85 10 Mg Al 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Mg_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Al_(0.05)O₂ 1680 94.1 85.1 11 Ga Al 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Ga_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Al_(0.05)O₂ 1670 94.5 84 12 Al Fe 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Al_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Fe_(0.05)O₂ 1690 93.6 84.3 13 Al Co 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Al_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Co_(0.05)O₂ 1710 94.1 83.9 14 Al Zn 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Al_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Zn_(0.05)O₂ 1700 94 84.2 15 Al Sn 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Al_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Sn_(0.05)O₂ 1700 94.2 84.9 16 Al Cr 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Al_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Cr_(0.05)O₂ 1710 94.4 84.3 17 Al V 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Al_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)V_(0.05)O₂ 1710 93.3 84.6 18 Al T1 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Al_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Ti_(0.05)O₂ 1680 94.1 84.4 19 Al Mg 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Al_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Mg_(0.05)O₂ 1690 94.7 84.5 20 Al Ga 50/50Li_(1.02)Ni_(0.70)Co_(0.25)Al_(0.05)O₂Li_(1.02)Ni_(0.65)Mn_(0.30)Ga_(0.05)O₂ 1670 94.2 84.7 Comparative 1 None— 100/0  Li_(1.02)Ni_(0.70)Co_(0.30)O₂ None 1820 88.1 59.2 example 2 —None  0/100 None Li_(1.02)Ni_(0.65)Mn_(0.35)O₂ 1510 95.9 86

It is known from the evaluation results summarized in Table 1 thatExamples 1 to 20, in which the cathode active material is composed ofthe mixture of the first lithium-transition metal composite oxide andthe second lithium-transition metal composite oxide, show improvedcapacity retention ratio after the 100th cycle in the atmospheres of 23°C. and 50° C. as compared with that of Comparative Example 1, in whichthe cathode active material is singly composed of the firstlithium-transition metal composite oxide.

Comparative Example 1 shows a case where the cathode active material issingly composed of the first lithium-transition metal composite oxide,and the cathode active material is not added with any compound composedof one or more transition metals or elements selected from Group 2, 3and 4 elements of the periodic table, and thereby causes deteriorationof crystal structure under repetitive charge/discharge, because thefirst lithium-transition metal composite oxide exhibits an unstablecrystal structure. Thus, the cathode active material singly composed ofthe first lithium-transition metal composite oxide causes degradation ofcharge/discharge cycle capacity retention ratio. In particular, theabove cathode active material remarkably degrades charge/discharge cyclecapacity retention ratio under high temperature environment, becausedeterioration of the crystal structure is promoted due to hightemperature and, besides, decomposition of the electrolyte is caused.

On the contrary, Examples 1 to 20 show that adding the secondlithium-transition metal composite oxide to the first lithium-transitionmetal composite oxide allows a change of crystal structure of thecathode active material in response to charge/discharge to be reduced,and results in suppression of degradation of crystal structure of thewhole cathode active material in response to the charge/discharge,because the second lithium-transition metal composite oxide exhibits astabled crystal structure. Thus, the cathode active material showsimproved capacity retention ratio after the 100th cycle in theatmospheres of 23° C. and 50° C.

It is also known from the evaluation results summarized in Table 1 thatExamples 1 to 20 show larger initial discharge capacity as compared withthat of Comparative Example 2, in which the cathode active material issingly composed of the second lithium-transition metal composite oxide.

Comparative Example 2 shows a case where the cathode active material issingly composed of the second lithium-transition metal composite oxide,and the cathode active material is not added with any compound composedof one or more transition metals or elements selected from Group 2, 3and 4 elements of the periodic table, and thereby causes lowering ofinitial discharge capacity, because the second lithium-transition metalcomposite oxide has low capacity.

On the contrary, Examples 1 to 20 show that adding the firstlithium-transition metal composite oxide to the secondlithium-transition metal composite oxide results in improvement ofinitial discharge capacity of the whole cathode active material, becausethe first lithium-transition metal composite oxide has large capacity.

As judged from the above, it is apparent that use of the cathode activematerial composed of the mixture of the first lithium-transition metalcomposite oxide and the second lithium-transition metal composite oxidein manufacture of the non-aqueous electrolyte secondary battery iseffective in raising the initial discharge capacity, increasing theenergy density and also in upgrading the charge/discharge cycle capacityretention ratio. Specifically, larger initial discharge capacity andimproved charge/discharge cycle capacity retention ratio may be alsoachieved, even though any transition metal or element selected fromGroup 2, 3 and 4 elements of the periodic table is not added to thefirst lithium-transition metal composite oxide and the secondlithium-transition metal composite oxide, like Example 1.

Next, Table 2 shows evaluation results of the initial dischargecapacity, the capacity retention ratio after the 100th cycle in theatmosphere of 23° C. and the capacity retention ratio after the 100thcycle in the atmosphere of 50° C. in Examples 1 and 21 to 24 andComparative Examples 3 and 4. It is to be noted that the additives M andM′ to be added to the first lithium-transition metal composite oxide andthe second lithium-transition metal composite oxide all represent Al inExamples 1 and 21 to 24 and Comparative Examples 3 and 4.

TABLE 2 Mixing ratio of first lithium- transition metal composite oxide(A) to second lithium- transition metal Initial Capacity retentioncomposite oxide (B) discharge ratio after 100th (% by weight) capacitycycle [%] (A)/(B) [mAh] 23° C. 50° C. Example 1 50/50 1700 9.52 84.5 2115/85 1610 95.4 85.5 22 30/70 1680 95.5 84.5 23 70/30 1710 93.3 83.3 2485/15 1720 91.8 73.9 Comparative 3 10/90 1540 96.1 86.8 Example 4 90/101740 89.3 61.3

It is known from the evaluation results summarized in Table 2 thatExamples 1 and 21 to 24, in which the mixing ratio of the firstlithium-transition metal composite oxide to the secondlithium-transition metal composite oxide was adjusted to 15% by weightor more to 85% by weight or less with respect to the whole cathodeactive material, show larger initial discharge capacity as compared withthat of Comparative Example 3, in which the first lithium-transitionmetal composite oxide and the second lithium transition-metal compositeoxide were mixed in a ratio of 10% by weight to 90% by weight.

Comparative Example 3 shows that use of a mixture of 10% by weight ofthe first lithium-transition metal composite oxide and 90% by weight ofthe second lithium-transition metal composite oxide for the cathodeactive material causes remarkable lowering of the initial dischargecapacity as compared with that of Examples 1 and 21 to 24, because thelow-capacity second lithium-transition metal composite oxide accountsfor a large percentage of the cathode active material.

On the contrary, Examples 1 and 21 to 24 show that adding the secondlithium-transition metal composite oxide in a ratio of 15% by weight ormore to 85% by weight or less with respect to the whole cathode activematerial results in larger initial discharge capacity, because thelarge-capacity first lithium-transition metal composite oxide iscontained in proper percent by weight with respect to the whole cathodeactive material. Examples 1 and 21 to 24 also show that the initialdischarge capacity increases with increasing first lithium-transitionmetal composite oxide in mixing ratio.

It is also known from the evaluation results summarized in Table 2 thatExamples 1 and 21 to 24 show improved capacity retention ratio after the100th cycle in the atmospheres of 23° C. and 50° C. as compared withthat of Comparative Example 4, in which 90% of the firstlithium-transition metal composite oxide and 10% of the secondlithium-transition metal composite oxide were mixed.

Comparative Example 4 shows that use of a mixture of 90% by weight ofthe first lithium-transition metal composite oxide and 10% by weight ofthe second lithium-transition metal composite oxide for the cathodeactive material promotes deterioration of the crystal structure underrepetitive charge/discharge and thereby causes degradation ofcharge/discharge cycle capacity retention ratio, because the firstlithium-transition metal composition oxide having the unstable crystalstructure accounts for a large percentage of the cathode activematerial. In particular, the above cathode active material causesremarkable degradation of capacity retention ratio after the 100th cyclein the atmosphere of 50° C., because deterioration of the crystalstructure is promoted under high temperature environment, and besides,degradation of the electrolyte is also caused.

On the contrary, Examples 1 and 21 to 24 show that adding the firstlithium-transition metal composite oxide in a ratio of 15% by weight ormore to 85% by weight or less by weight with respect to the wholecathode active material allows a change of crystal structure of thecathode active material in response to charge/discharge to besuppressed, and results in improvement of charge/discharge cyclecapacity retention ratio, because the first lithium-transition metalcomposite oxide is added in proper percent by weight with respect to thewhole cathode active material.

As judged from the above, it is known that use of the cathode activematerial, in which the first lithium-transition metal composite oxide isadded in a ratio of 15% by weight or more to 85% by weight or less withrespect to the whole cathode active material, in manufacture of thenon-aqueous electrolyte secondary battery is successful in raisinginitial discharge capacity and also in improving charge/discharge cyclecapacity retention ratio.

Next, Table 3 shows evaluation results of the initial dischargecapacity, the capacity retention ratio after the 100th cycle in theatmosphere of 23° C. and the capacity retention ratio after the 100thcycle in the atmosphere of 50° C. in Examples 1 and 27 to 32 andComparative Examples 5 to 8. It is to be noted that a firstlithium-transition metal composite oxide and second lithium-transitionmetal composite oxide are mixed in a ratio of 50% by weight to 50% byweight.

TABLE 3 Mean particle size [μm] First Second lithium- lithium-transition transition Initial Capacity retention metal metal dischargeratio after 100th composite composition capacity cycle [%] oxide oxide[mAh] 23° C. 50° C. Example 1 15 15 1700 95.2 84.5 25 2 15 1730 92.983.2 26 8 15 1690 94.8 85.1 27 20 15 1710 95.4 84.6 28 30 15 1700 91.780 29 15 2 1720 93.3 84.5 30 15 9 1720 94.5 83.9 31 15 18 1710 92.9 85.332 15 30 1700 93 82.1 Com- 5 1 15 1720 87.9 78.4 parative 6 40 15 171084.7 62.2 Example 7 15 1 1730 89.2 79.1 8 15 40 1690 81.5 60.5

It is known from the evaluation results summarized in Table 3 thatExamples 1 and 27 to 32, in which the mean particle size of each of thefirst lithium-transition metal composite oxide and the secondlithium-transition metal composite oxide was adjusted to a range of 2 μmor more to 30 μm or less, show improved capacity retention ratio afterthe 100th cycle in the atmosphere of 50° C. as compared with that ofComparative Examples 5 to 8, in which either one of the firstlithium-transition metal composite oxide and the secondlithium-transition metal composite oxide was adjusted to have the meanparticle size of 1 μm or 40 μm, while the average mean particle of theother was adjusted to 15 μm.

Comparative Examples 5 to 8 show that adjusting the mean particle sizeof either one of the first lithium-transition metal composite oxide andthe second lithium-transition metal composite oxide to less than 2 μmwhile adjusting the other to 15 μm promotes decomposition of theelectrolyte and thereby causes more degradation of cycle capacityretention ratio in the atmosphere of 50° C. as compared with that ofExamples 1 and 27 to 32, because a contact area between the cathodeactive material and the electrolyte solution is increased in excess. Anincrease to more than 30 μm in mean particle size makes it difficult tosufficiently mix the first lithium-transition metal composite oxide andthe second lithium-transition metal composite oxide, and thereby causesdegradation of cycle capacity retention ratio, particularly, degradationof cycle capacity retention ratio in the atmosphere of 50° C.

On the contrary, Examples 1 and 25 to 28 show that use of the mixture ofthe first lithium-transition metal composite oxide obtained by adjustingthe mean particle size to a range of 2 μm or more to 30 μm or less andthe second lithium-transition metal composite oxide obtained byadjusting the mean particle size constant as much as 15 μm for thecathode active material allows the contact area between the cathodeactive material and the electrolyte solution to be reduced, and resultsin sufficient mixing of the first lithium-transition metal compositeoxide and the second lithium-transition metal composite oxide. Thus,Examples 1 and 25 to 28 show more improved capacity retention ratioafter the 100th cycle in the atmosphere of 50° C. as compared with thatof Comparative Examples 5 to 8.

As judged from the above results, it is known that use of the cathodeactive material, in which the mean particle size of the firstlithium-transition metal composite oxide and the secondlithium-transition metal composite oxide was adjusted to a range of 2 μmor more to 30 μm or less, in manufacture of the non-aqueous electrolytesecondary battery is successful in improving the charge retention ratioafter 100th cycle in the atmosphere of 50° C.

Table 4 shows evaluation results of the initial discharge capacity, thecapacity retention ratio after the 100th cycle in the atmosphere of 23°C. and the capacity retention ratio after the 100th cycle in theatmosphere of 50° C. in Examples 1 and 33 to 36 and Comparative Examples9 to 12. It is to be noted that a first lithium-transition metalcomposite oxide and second lithium-transition metal composite oxide aremixed in a ratio of 50% by weight to 50% by weight.

TABLE 4 Co Mn parts y in parts t in first second lithium- lithium-transition transition Initial Capacity retention metal metal dischargeratio after 100th composite composite capacity cycle [%] oxide oxide[mAh] 23° C. 50° C. Example 1 0.25 0.3 1700 95.2 84.5 33 0.05 0.3 175091.9 82.4 34 0.5 0.3 1640 96.3 85.7 35 0.25 0.05 1770 93.4 83.1 36 0.250.5 1630 96 86.3 Comparative 9 0.01 0.3 1810 82.2 53.9 Example 10 0.60.3 1310 96.8 85.1 11 0.25 0.01 1820 81.7 56.8 12 0.25 0.6 1290 95.887.2

It is known from the evaluation results summarized in Table 4 thatExamples 1 and 33 to 36, in which Co parts y in the firstlithium-transition metal composite oxide (LiNiCoMO₂) and Mn parts t inthe second lithium-transition metal composite oxide (LiNiMnMO₂) wereadjusted to a range of 0.05 or more to 0.50 or less, show more improvedcapacity retention ratio after the 100th cycle in the atmosphere of 50°C. as compared with that of Comparative Example 9, in which y was lessthan 0.05 or Comparative Example 11, in which t was less than 0.05.

Comparative Example 9 shows a case where the Co parts y in the firstlithium-transition metal composite oxide were adjusted to 0.01, whileComparative Example 11 shows a case where the Mn parts t in the secondlithium-transition metal composite oxide were adjusted to 0.01. Asdescribed above, Comparative Example 9 or 11 show that adjusting Coparts y in the first lithium-transition metal composite oxide to 0.01,or Mn parts t in the second lithium-transition metal composite oxide to0.01 renders the crystal structures thereof unstable, and thereby causesdeterioration of crystal structure of the cathode active material underrepetitive charge/discharge, and also degradation of charge-dischargecycle capacity retention ratio. In particular, the cathode activematerial causes remarkable degradation of capacity retention ratio afterthe 100th cycle in the atmosphere of 50° C., because deterioration ofthe crystal structure is promoted under high temperature environment.

On the contrary, Examples 1 and 33 to 36 show that adjusting Co parts yin the first lithium-transition metal composite oxide and Mn parts t inthe second lithium-transition metal compound oxide (LiNiMnMO) to a rangeof 0.05 or more to 0.50 or less allows the crystal structures of thefirst lithium-transition metal composite oxide and the secondlithium-transition metal composite oxide to be stabled, and therebyachieves excellent charge/discharge cycle capacity retention ratio evenunder high temperature environment.

It is also known from the evaluation results in Table 4 that Examples 1and 33 to 36 show larger initial discharge capacity as compared withthat of Comparative Example 10, in which Co parts y in the firstlithium-transition metal composite oxide (LiNiCoMO) exceed 0.50 orComparative Example 12, in which Mn parts t in the secondlithium-transition metal composite oxide (LiNiMnMO) exceed 0.50.

Comparative Example 10 shows a case where the first lithium-transitionmetal composite oxide, in which Co parts y were adjusted to 0.60, wasused, and Comparative Example 12 shows a case where the secondlithium-transition metal composite oxide, in which Mn parts t wereadjusted to 0.60, was used. Adjusting Co and Mn parts to more than 0.5lowers the capacity of the whole cathode active material, and therebycauses lowering of the initial discharge capacity, like ComparativeExamples 10 to 12.

On the contrary, Examples 1 and 33 to 36 show that adjusting Co parts yin the first lithium-transition metal composite oxide and Mn parts t inthe second lithium-transition metal composite oxide to a range of 0.05or more to 0.50 or less allows the crystal structure to be stabled, andthereby achieves larger initial discharge capacity.

As judged from the above, it is known that adjusting Co parts in thefirst lithium-transition metal composite oxide and Mn parts in thesecond lithium-transition metal composite oxide to a range of 0.05 ormore to 0.50 or less in manufacture of the non-aqueous electrolytesecondary battery is successful in raising the initial dischargecapacity and in improving the charge/discharge cycle characteristics.

Some embodiments of a lithium ion non-aqueous secondary battery as asecond aspect of the present invention will next be described withreference to the accompanying drawings.

FIG. 2 is a sectional view showing an embodiment of the lithium ionnon-aqueous electrolyte secondary battery according to the presentinvention. As shown in FIG. 2, the non-aqueous electrolyte secondarybattery is configured so that a spirally wound electrode member 210obtained by stacking and further spirally rolling up a long strip-shapedcathode 211 and a long strip-shaped anode 212 while placing a separator213 in between is enclosed, with insulator plates 202 mounted to upperand lower sides of the electrode member, in a battery container 201.

A battery cap 204 is also mounted to the battery container 201 bycaulking the battery container while placing a gasket 207 in between.The battery cap 204 is electrically connected to the cathode 211 througha cathode lead 215, and provides functions as a cathode of this battery.Meanwhile, the anode 212 is electrically connected to a bottom of thebattery container 201 through an anode lead 216 and configured to allowthe battery container 201 to function as an anode of this battery.

Specifically, this battery has a center pin 214 in the center of thespirally wound electrode member 210, and a safety valve 205 having adisk plate 205 a and providing current interrupt functions is a safetydevice for releasing an electrical connection so as to allow a portionelectrically connected to the cathode lead 215 to be deformed when apressure inside the battery is increased.

A thermo-sensitive resistance element 206 placed between the safetyvalve 205 and the battery cap 204 provides functions as an in-batteryelement for interrupting a current when a charge/discharge stateexceeding a maximum rated current occurs and/or the battery is exposedto high temperature.

FIG. 3 shows a structure of the above long strip-shaped cathode 211. Asshown in FIG. 3, the long strip-shaped cathode 211 is configured so thatthe opposite faces (surface and back surface) of a long strip-shapedcathode current collector 211 a are coated with cathode active materialcompound layers 211 b and 211 c.

In the non-aqueous electrolyte secondary battery of the presentinvention, it is preferable to use effectively the inside of the batteryso as to increase an energy density of an obtained non-aqueouselectrolyte secondary battery by reducing an active material massirrelevant to a battery reaction, as will be described later, in such amanner as that edges of the cathode active material compound layers 211b and 211 c are arranged not to be flush in a longitudinal direction atboth or one of the ends of the long strip-shaped cathode 211, as shownin the figure.

Although an anode structure is not shown, the long strip-shaped anode212 also has the same structure as the long strip-shaped cathode 211,and produces the same effects as the above in such a manner as thatedges of the anode active material compound layers coated on theopposite faces of a current collector are arranged not to be flush asviewed from a side face thereof.

While the above compound layer edge treatment of at least one of thecathode and the anode is enough to obtain the above effects, it is alsoallowable to treat the edges of the compound layers for both of thecathode and the anode.

FIG. 4 is a sectional view taken along line A-A of the non-aqueouselectrolyte secondary battery shown in FIG. 2, and there is shown thespirally wound electrode member 210.

In FIG. 4, the spirally wound electrode member 210 is configured so thata four-layer stacked structure obtained by stacking a long strip-shapedanode 212, a separator 213 (not shown), a long strip-shaped cathode 211and a separator 213 (not shown) in this order is spirally wound up withthe long strip-shaped anode 212 placed on the inner side (the center) ofthe electrode member 210. The long strip-shaped cathode 211 and the longstrip-shaped anode 212 are arranged so that the compound layers 211 c,212 c are on the inner side (center side) of the spirally woundelectrode member 210, while the compound layers 211 b, 212 b are on theouter side thereof (See FIG. 3).

In thus-configured spirally wound electrode member, a width (height inFIG. 2) and a length (winding-up length), that is, a reaction area ofthe anode 212 arranged in parallel to the cathode 211 with the separator213 (not shown) placed in between is set to be greater than a width anda length (reaction area) of the cathode 211 in order to prevent innershort-circuiting caused by deposition of lithium during charging.

Specifically, the spirally wound electrode member shown in the drawingis obtained in a typical winding-up form, in which no treatment isapplied to the compound layer edges of the long strip-shaped cathode 211and the long strip-shaped anode 212 so that the edges of the cathodeactive material compound layers 211 b, 211 c and the edges of the anodeactive material compound layers 212 b, 212 c are flushed, as viewed froma side face thereof.

FIG. 5 shows a spirally wound electrode member obtained in a differentwinding-up form.

The spirally wound electrode member shown in FIG. 5 is configured sothat the anode active material compound layer at one end of the longstrip-shaped anode 212, specifically, at an end forming the outermostperiphery of the spirally wound electrode member is provided on one sideonly. In other words, the outer periphery of the spirally woundelectrode member is provided with only an inner-side compound layer 212c of the anode, and has no outer-side compound layer 212 b. It is to benoted that, use of the above winding-up form, in which no treatment isapplied to the opposite ends of the long strip-shaped cathode 211 sothat the inner-side compound layer 211 c and the outer-side compoundlayer 211 b are flushed at the opposite ends of the long strip-shapedcathode 211, makes it possible to allow only a cathode active materialcompound layer portion and an anode active material compound layerportion, which are actually participating in the battery reaction, to beplaced inside the battery, and thereby enables effective use of theinside of the battery so as to increase an energy density of an obtainednon-aqueous electrolyte secondary battery.

FIG. 6 shows a spirally wound electrode member obtained in a differentwinding-up form, in which the other end (innermost end) of the longstrip-shaped anode 212 is provided with only the outer-side compoundlayer 212 b, and one end (outermost end) of the long strip-shapedcathode 211 is provided with only the inner-side compound layer 211 c.It is to be noted that, the compound layers are flushed at one end(outermost end) of the long strip-shaped anode 212 and the other end(innermost end) of the long strip-shaped cathode.

Use of the above winding-up form also enables effective use of theinside of the battery so as to increase an energy density of an obtainedbattery.

FIG. 7 shows a spirally wound electrode member obtained in a furtherdifferent winding-up form, in which one end (outermost end) of the longstrip-shaped cathode 211 is provided with only the inner-side compoundlayer 211 c, and the cathode active material compound layers are flushedat the other end (innermost end) of the cathode 211. It is to be notedthat, the long strip-shaped anode 212 is configured so that the anodeactive material compound layers are flushed at the opposite ends of theanode 212.

Furthermore, FIG. 8 shows a spirally wound electrode member obtained ina different winding-up form, in which the other end (innermost end) ofthe long strip-shaped cathode 211 is provided with only the outer-sidecompound layer 211 b, and one end (outermost end) thereof is providedwith only the inner-side compound layer 211 c. Use of the winding-upform, in which the anode 212 is configured so that the anode activematerial compound layers are flushed at the opposite ends of the anode212 as shown in FIGS. 7 and 8, also enables effective use of the insideof the battery so as to increase an energy density of an obtainedbattery.

While Examples of the present invention will next be described in moredetail, the present invention is by no means limited to these Examples.

Example 37

First, how to prepare the cathode active material used in this Examplewill next be described.

Nickel nitrate, cobalt nitrate and manganese nitrate, which arecommercially available materials, were mixed as a solution in a ratio ofNi to Co to Mn of 0.50:0.20:0.30, and added with aqueous ammonia whilesufficiently stirring a mixture to prepare a composite hydroxide. Thecomposite hydroxide was added with lithium hydroxide, sintered in anoxygen atmosphere of 850° C. for 10 hours, and pulverized to obtain alithium-transition metal composite oxide in a powdered form. Analysis ofthus-obtained powder was carried out using an atomic absorptionspectrometry technology, and results of the analysis confirmed acomposition of LiNi_(0.5)Co_(0.2)Mn_(0.30)O₂. Measurement of theparticle size was also carried out using a laser diffraction technology,and results of the measurement confirmed that the above powder has amean particle size of 13 μm.

Further, X-ray diffraction measurement of the above powder was carriedout, and results of the measurement confirmed that an obtained patternis similar to a LiNiO₂ pattern defined in 09-0063 of ICDD, and also thatthe above powder exhibits a layer halite structure similar to that ofLiNiO₂. Observation of the above powder was also carried out using SEMand results of the observation confirmed spherical particles consistingof aggregations of primary grains of 0.1 to 51 μm.

Then, 86% of lithium-transition metal composite oxide thus prepared, 10%of graphite as a conductive material, and 4% of polyvinylidene fluoride((PVdF) as a binder were mixed, and further added withN-methyl-2-pyrolidone (NMP) to be dispersed therein to prepare acompound material in a slurry form. The slurry-formed compound materialwas uniformly coated on a long strip-shaped aluminum foil of 20 μmthick, dried, compressed using a roller press machine and then punchedout in a predetermined size to obtain a pellet.

Thus-fabricated pellet was used as a cathode, while a lithium foil wasused as an anode, and these electrodes were stacked while placing aknown porous polyolefin film in between to manufacture a coil cellhaving a diameter of 20 mm and a height of 1.6 mm.

Herein, for the electrolyte solution, a non-aqueous electrolyte solutionwas prepared by dissolving LiPF₆ in a solution obtained by mixingethylene carbonate and methyl ethyl carbonate in a volume mixing ratioof 1:1 so as to adjust the concentration thereof to 1 mol/dm³.

Thus-manufactured coin cell was charged up to a point of extraction of50% of the whole lithium contents, disassembled to take out the pellet,and subjected to XAFS measurement, and XAFS measurement of a non-chargedpellet was also carried out. In XAFS measurement, X-ray absorptionspectrum was measured using a through transmission technology with Si(111) for dispersive crystal and by scanning between 7960 eV and 9100 eVas X-ray energy.

FIG. 9 shows results of measurement of a non-charged product and a50%-charged product, in which a range of 8190 eV to 8220 eV ofabsorption spectrum standardized with jump height of absorption edge asreference after subtraction of a background is shown in anenlarged-scale. When the focus is placed on a position of 0.5 inabsorbance, shift of 2.2 eV was observed between the non-charged productand the 50% charged product.

A cylindrical non-aqueous electrolyte secondary battery was manufacturedby using the above lithium-transition metal composite oxide for thecathode active material and subjected to evaluation on cyclecharacteristics under high temperature environment.

Specifically, 86% of cathode active material, 10% of graphite as aconductive material and 4% of polyvinylidene fluoride (PVdF) as a binderwere mixed, and further dispersed into N-methyl-2-pyrolidone (NMP) toprepare a cathode compound material of a slurry form. The slurry-formedcompound material was uniformly coated on the opposite faces of a longstrip-shaped aluminum foil of 20 μm thick, dried, and compressed using aroll press machine to thereby obtain a long strip-shaped cathode.

Next, for an anode, to 90% of artificial graphite in a powdered form wasadded 10% of PVdF, and further dispersed into NMP to prepare an anodecompound material in a slurry form. The slurry-formed compound materialwas uniformly coated on the opposite faces of a copper foil of 10 μmthick, dried and compressed using a roll press machine to thereby obtaina long strip-shaped anode.

Thus-fabricated long strip-shaped cathode and long strip-shaped anodewere spirally wound up a large number of times while placing a porouspolyolefin film in between to fabricate a spirally wound electrodemember. Thus-fabricated electrode member was enclosed in a batterycontainer made of nickel-plated iron, and insulator plates were mountedto both upper and lower faces of the electrode member.

Then, a cathode lead made of aluminum was extracted from a cathodecurrent collector and welded to a projection part of a safety valvewhose electrical connection to the battery cap has been ensured, and ananode lead made of nickel was extracted from an anode current collectorand welded to a bottom of the battery container.

Meanwhile, for the electrolyte solution, a non-aqueous electrolytesolution was prepared by dissolving LiPF₆ in a solution obtained bymixing ethylene carbonate and methyl ethyl carbonate in a volume mixingratio of 1:1 so as to adjust the concentration thereof to 1 mol/dm³.

Finally, the electrolyte solution was poured into the battery containerwith the above electrode member incorporated therein, and the safetyvalve, the PTC element and the battery cap were fixed by caulking thebattery container while placing an insulator sealing gasket in betweento thereby manufacture a cylindrical battery having an outer diameter of18 mm and a height of 65 mm.

Thus-fabricated non-aqueous electrolyte secondary battery was subjectedto measurement of initial discharge capacity under conditions that thebattery was charged under a voltage of 4.20 V and a current of 1000 mAin an atmosphere of 45° C. for 2.5 hours, and discharged under a currentof 800 mA and a cutoff voltage of 2.75 V. Measurement of relativedischarge capacity after the 100th cycle was also carried out byrepeating the charge/discharge cycle under the same conditions as thosefor measurement of the initial discharge capacity, so as to calculate aretention ratio to the initial discharge capacity.

Comparative Example 13

A lithium-transition metal composite oxide LiNi_(0.8)Co_(0.2)O₂ wasprepared by repeating operations similar to those of Example 37, exceptthat a mixing ratio of materials was altered and sintering temperaturewas set at 750° C.

The XAFS measurement was carried out similarly, and resulted in a shiftwidth of 0.8 eV, as shown in FIG. 10. Except for using thislithium-transition metal composite oxide, the non-aqueous electrolytesecondary battery was manufactured similarly to Example 37, and a cycleretention ratio in an atmosphere of 45° C. similar to that in Example 37was evaluated.

Example 38

A lithium-transition metal composite oxide LiNi_(0.60)Co_(0.20)O₂ wasprepared by repeating operations similar to those of Example 37, exceptthat a mixing ratio of materials was altered.

The XAFS measurement was carried out similarly, and resulted in a shiftwidth of 1.9 eV. Except for using this lithium-transition metalcomposite oxide, the non-aqueous electrolyte secondary battery wasmanufactured similarly to Example 37, and a cycle retention ratio in anatmosphere of 45° C. similar to that in Example 37 was evaluated.

Example 39

A lithium-transition metal composite oxideLiNi_(0.70)Co_(0.20)Ti_(0.10)O₂ was prepared by repeating operationssimilar to those of Example 37, except that titanium oxide was used inplace of manganese carbonate for materials, a mixing ratio of thematerials was altered and sintering temperature was set at 7500C.

The XAFS measurement was carried out similarly and resulted in a shiftwidth of 1.5 eV. Except for using this lithium-transition metalcomposite oxide, the non-aqueous electrolyte secondary battery wasmanufactured similarly to Example 37, and a cycle retention ratio in anatmosphere of 45° C. similar to that in Example 37 was evaluated.

Example 40

A lithium-transition metal composite oxideLiNi_(0.6)Co_(0.20)Mn_(0.10)Ti_(0.10)O₂ was prepared by repeatingoperations similar to those of Example 37, except that titanium oxidewas further added as materials, and a mixing ratio of the materials wasaltered.

The XAFS measurement was carried out similarly and resulted in a shiftwidth of 1.8 eV. Except for using this lithium-transition metalcomposite oxide, the non-aqueous electrolyte secondary battery wasmanufactured similarly to Example 37, and a cycle retention ratio in anatmosphere of 45° C. similar to that in Example 37 was evaluated.

Example 41

A lithium-transition metal composite oxide LiNi_(0.80)Co_(0.2)O₂ wasprepared by repeating operations similar to those of Example 37, exceptthat a mixing ratio of materials was altered, and sintering temperaturewas set at 800° C.

The XAFS measurement was carried out similarly and resulted in a shiftwidth of 1.2 eV. Except for using this lithium-transition metalcomposite oxide, the non-aqueous electrolyte was manufactured similarlyto Example 37, and a cycle retention ratio in an atmosphere of 45° C.similar to that in Example 37 was evaluated.

Example 42

A lithium-transition metal composite oxide LiNi_(0.60)Co_(0.40)O₂ wasprepared by repeating operations similar to those of Example 37, exceptthat a mixing ratio of materials was altered and sintering temperaturewas set at 750° C.

The XAFS measurement was carried out similarly and resulted in a shiftwidth of 1.3 eV. Except for using this lithium-transition metalcomposite oxide, the non-aqueous electrolyte secondary battery wasmanufactured similarly to Example 37, and a cycle retention ratio in anatmosphere of 45° C. similar to that in Example 37 was evaluated.

Example 43

A lithium-transition metal composite oxide LiNi_(0.80)Co_(0.20)O₂ wasprepared by repeating operations similar to those of Example 37, exceptthat a mixing ratio of materials was altered, sintering temperature wasset at 750° C., and an atmosphere in sintering was changed from oxygento air.

The XAFS measurement was carried out similarly and resulted in a shiftwidth of 1.4 eV.

Except for using this lithium-transition metal composite oxide, thenon-aqueous electrolyte secondary battery was manufactured similarly toExample 37, and a cycle retention ratio in an atmosphere of 45° C.similar to that in Example 37 was evaluated.

Comparative Example 14

A lithium-transition metal composite oxideLiNi_(0.85)Co_(0.10)Al_(0.05)O₂ was prepared by repeating operationssimilar to those of Example 37, except that a mixing ratio of materialswas altered, and sintering temperature was set at 7500C.

The XAFS measurement was carried out similarly and resulted in a shiftwidth of 0.7 eV. Except for using this lithium-transition metalcomposite oxide, the non-aqueous electrolyte secondary battery wasmanufactured similarly to Example 37, and a cycle retention ratio in anatmosphere of 45° C. similar to that in Example 37 was evaluated.

TABLE 5 Shift Capacity Synthesis conditions width retention CompositionTemperature Atmosphere [eV] ratio (%) Example 37LiNio_(.50)Co_(0.20)Mn_(0.3)O₂ 850° C. Oxygen 2.2 92.4 38LiNi_(0.6)Co_(0.2)Mn_(0.202) 850° C. Oxygen 1.9 91 39LiM_(0.70)Co_(0.20)Tio_(.20)O₂ 750° C. Oxygen 1.5 90 40LiNi_(0.60)Co_(0.20)Mn_(0.1)Ti_(0.10)O₂ 850° C. Oxygen 1.8 91.1 41LiNi_(0.80)Co_(0.20)O₂ 800° C. Oxygen 1.2 85.6 42 LiNi_(0.60)Co_(0.40)O₂750° C. Oxygen 1.3 86.4 43 LiNio_(.80)Co_(0.20)O₂ 750° C. Air 1.4 86.8Comparative 13 LiNi_(0.80)Co_(0.20)O₂ 750° C. Oxygen 0.8 71.9 Example 14LiNi_(0.85)Co_(0.10)A_(0.05)O₂ 750° C. Oxygen 0.7 70.3

As judged from the above results, it was confirmed that regulating ashift width to 1.0 eV or more results in great improvement of cyclecharacteristics under high temperature environment. It was alsoconfirmed that adding at least one element selected from Mn and Tiincreases a shift width in particular, and results in furtherimprovement of cycle characteristics under high temperature environment.

While the present invention has been described in detail with referenceto some preferred embodiments, it is to be understood that the presentinvention is by no means limited to the above embodiments, and variousmodifications are possible without departing from the spirit and scopeof the present invention. In other words, means for embodying thepresent invention is not limited in particular, and the presentinvention may be also embodied based on investigations of synthesisconditions in synthesizing the lithium-transition metal composite oxide,use of different species of elements as additives and parts ofcomponents, for instance.

Next, some embodiments of a lithium ion non-aqueous electrolytesecondary battery of the present invention will be specificallydescribed with reference to the accompanying drawings.

FIG. 11 is a sectional view showing an embodiment of a lithium ionnon-aqueous electrolyte secondary battery of the present invention. Asshown in FIG. 11, the non-aqueous electrolyte secondary battery isconfigured so that a spirally wound electrode member 310 obtained bystacking and further spirally rolling up a long strip-shaped cathode 311and a long strip-shaped anode 312 while placing a separator 313 inbetween is enclosed, with insulator plates 302 mounted to upper andlower sides of the electrode member, in a battery container 301.

A battery cap 304 is also mounted to the battery container 301 bycaulking the battery container while placing a gasket 307 in between.The battery cap 304 is electrically connected to the cathode 311 througha cathode lead 315 and provides functions as a cathode of this battery.Meanwhile, the anode 312 is electrically connected to a bottom of thebattery container 301 through an anode lead 316, and configured to allowthe battery container 301 to function as an anode of this battery.

Specifically, this battery has a center pin 314 in the center of thespirally wound electrode member 310, and a safety valve 305 providingcurrent interrupt functions and having a disk plate 305 a is a safetydevice for releasing an electrical connection so as to allow a portionelectrically connected to the cathode lead 315 to be deformed when apressure inside the battery is increased.

A thermo-sensitive resistance element 306 placed between the safetyvalve 305 and the battery cap 304 provides functions as an in-batteryelement for interrupting a current when a charge/discharge stateexceeding a maximum rated current occurs and/or the battery is exposedto high temperature.

FIG. 12 shows a structure of the above long strip-shaped cathode 311. Asshown in FIG. 12, the long strip-shaped cathode 311 is configured sothat the opposite faces (surface and back surface) of a longstrip-shaped cathode current collector 311 a are coated with cathodeactive material compound layers 311 b and 311 c.

As shown in the drawing, in the non-aqueous electrolyte secondarybattery of the present invention, it is preferable to effectively usethe inside of the battery so as to increase an energy density of anobtained non-aqueous electrolyte secondary battery by reducing an activematerial mass irrelevant to a battery reaction in such a manner as thatedges of the cathode active material compound layers 311 b and 311 c arearranged to be irregular in a longitudinal direction of both or one ofthe ends of the long strip-shaped cathode 311, as will be describedlater.

Although an anode structure is not shown, the long strip-shaped anode312 also has the same structure as the long strip-shaped cathode 311,and produces the same effects as the above in such a manner as thatedges of the anode active material compound layers coated on theopposite faces of a current collector are arranged not to be flush asviewed from a side face thereof, like the arrangement of the cathode.

It is to be noted that, while the above compound layer edge treatment ofat least one of the cathode and the anode is enough to obtain the aboveeffects, it is also allowable to treat the edges of the compound Ulayers for both of the cathode and the anode.

FIG. 13 is a sectional view taken along line A-A of the non-aqueouselectrolyte secondary battery shown in FIG. 11, and the spirally woundelectrode member 310 is shown.

In FIG. 13, the spirally wound electrode member 310 is configured sothat a four-layer stacked structure obtained by stacking on an eleventhsection a long strip-shaped anode 312, a separator 313 (not shown), along strip-shaped cathode 311 and a separator 313 (not shown) isspirally wound up with the long strip-shaped anode 312 placed on theinner side (center portion) of the electrode member 310. The longstrip-shaped cathode 311 and the long strip-shaped anode 312 arearranged so that the compound layers 311 c and 312 c thereof are on theinner side (center side) of the spirally wound electrode member 310,while the compound layers 311 b and 312 b thereof are on the outer sidethereof (See FIG. 12).

In general, in thus-configured spirally wound electrode member, a width(height in FIG. 11) and a length (winding-up length), that is, areaction area of the anode 312 arranged in parallel to the cathode 311while placing the separator 313 (not shown) in between is set so as tobe greater than a width and a length (reaction area) of the cathode 311in order to prevent inside short-circuiting caused by deposition oflithium during charging.

It is to be noted that, the spirally wound electrode member shown in thedrawing is obtained in a typical winding-up form, in which no treatmentis applied to the compound layer edges of the long strip-shaped cathode311 and the long strip-shaped anode 312 so that the edges of the cathodeactive material compound layers 311 b, 311 c and edges of the anodeactive material compound layers 312 b, 312 c are flushed, as viewed froma side face thereof.

FIG. 14 shows a spirally wound electrode member obtained in a differentwinding-up form.

The spirally wound electrode member shown in FIG. 14 is configured sothat the anode active material compound layer at one end of the longstrip-shaped anode 312, that is, at an end forming the outermostperiphery of the spirally wound electrode member is provided on one sideonly. In other words, the outermost periphery of the spirally woundelectrode member is provided with only an inner-side compound layer 312c of the anode, and has no outer-side compound layer 312 b.Incidentally, use of the above winding-up form, in which no treatment isapplied to the opposite ends of the long strip-shaped cathode 311 sothat the inner-side compound layer 311 c and the outer-side compoundlayer 311 b are flushed at the opposite ends of the cathode, allows onlya cathode active material compound layer portion and an anode activematerial compound layer portion, which are actually participating in thebattery reaction, to be placed on the inside of the battery, and therebyenables effective use of the inside of the battery so as to increase anenergy density of an obtained non-aqueous electrolyte secondary battery.

FIG. 15 shows a spirally wound electrode member obtained in a differentwinding-up form, in which the other end (innermost end) of the longstrip-shaped anode 312 is provided with only the outer-side compoundlayer 312 b, and one end (outermost end) of the long strip-shapedcathode 311 is provided with only the inner-side compound layer 311 c.Incidentally, the compound layers are flushed at one end (outermost end)of the long strip-shaped anode 312 and the other end (innermost end) ofthe long strip-shaped cathode.

Use of the above winding-up form also enables effective use of theinside of the battery similarly to the above so as to increase an energydensity of an obtained battery.

FIG. 16 shows a battery obtained in a further different winding-up form,in which one end (outermost end) of the long strip-shaped cathode 311 isprovided with only the inner-side compound layer 311 c, and the cathodeactive material compound layers are flushed at the other end (innermostend) of the cathode.

It is to be noted that the long strip-shaped anode 312 is configured sothat anode active material compound layers are flushed at the oppositeends of the anode.

Furthermore, FIG. 17 shows a spirally wound electrode member obtained ina different winding-up form, in which the other end (innermost end) ofthe long strip-shaped cathode 311 is provided with only the outer-sidecompound layer 311 b, and one end (outermost end) thereof is providedwith only the inner-side compound layer 311 c. Use of the winding-upform, in which the long strip-shaped anode 312 is configured so that theanode active material compound layers are flushed at the opposite endsof the anode 312 as shown in FIGS. 16 and 17, also enables effective useof the inside of the battery similarly to the above so as to increase anenergy density of an obtained battery.

EXAMPLES

While the present invention will be next described specifically on thebasis of Examples and Comparative Examples, it is to be understood thatthe present invention is by no means limited to these Examples.Incidentally, a cylindrical battery was manufactured and subjected toevaluation on over-discharge resistance of a secondary battery using thecathode active material of the present invention.

Example 44 (1) Preparation of First Lithium-Transition Metal CompositeOxide A

Cobalt oxide and lithium carbonate, which are commercially availablematerials, were mixed so that a molar ratio of Li to Co becomes1.02:1.00, and a mixture was put into a crucible made of alumina, andsintered in an atmosphere of dried air. Quantitative analysis ofthus-obtained powder was carried out using an atomic absorptionspectrometry technology, and results of the analysis confirmed acomposition of LiCoO₂. Also, measurement of a particle size was carriedout using a laser diffraction technology, and results of the measurementconfirmed that the above powder has a mean particle size of 15 μm.Further, X-ray diffraction measurement of the above powder was carriedout, and results of the measurement confirmed that an obtaineddiffraction pattern is similar to a LiCoO=pattern defined in 36-1004 ofInternational Center for Diffraction Data (which will be referred simplyto as ICDD) and also that the above powder exhibits a layer structuresimilar to that of LiCoO₂.

Then, 86% of lithium-transition metal composite oxide A thus-prepared,10% of graphite as a conductive material and 4% of polyvinylidenefluoride (which will be simply referred to as “PVdF”) as a binder weremixed and further dispersed into N-methyl-2-pyrolidone (which will besimply referred to as “NMP”) to obtain a compound material in a slurryform. The slurry-formed compound material was uniformly coated on a longstrip-shaped aluminum foil of 20 μm thick, dried, compressed using aroll press machine and punched out in a predetermined size to therebyobtain a pellet. The pellet was used as a cathode, while a lithium foilwas used as an anode, and these electrodes were stacked while placing aknown porous polyolefin film in between to thereby manufacture a coilcell having a diameter of 20 mm and a height of 1.6 mm. For theelectrolyte solution, a non-aqueous electrolyte solution was prepared bydissolving LiPF₆ in a solution obtained by mixing ethylene carbonate andmethyl ethyl carbonate in a volume mixing ratio of 1:1 so as to adjustthe concentration thereof to 1 mol/dm³.

Then, thus-fabricated coil cell was charged up to 4.250 V, thendischarged under a constant current of 0.2 C down to 3.000 V, andresulted in a mean discharge voltage of 3.948 V.

(2) Preparation of Second Lithium-Transition Metal Composite Oxide B

Nickel nitrate, cobalt nitrate and manganese nitrate, which arecommercially available materials, were mixed so as to have a solution ina molar ratio of Ni to Co to Mn of 0.60:0.20:0.20, and further addedwith aqueous ammonium drops while sufficiently stirring a mixture toprepare a composite hydroxide. The composite hydroxide was mixed withlithium hydroxide, sintered in an atmosphere of oxygen at 800° C. for 10hours, and pulverized to thereby prepare a lithium-transition metalcomposite oxide B in a powdered form. Analysis of thus-obtained powderwas carried out using an atomic absorption spectrometry technology, andresults of the analysis confirmed a composition ofLiNi_(0.5)Co_(0.2)Mn_(0.30)O₂. Measurement of a particle size was alsocarried out using a laser diffraction technology, and results of themeasurement confirmed that the above powder has a mean particle size of12 μm.

Further, X-ray diffraction measurement of the above powder was carriedout and results of the measurement confirmed that an obtaineddiffraction pattern is similar to a LiNiO₂ pattern defined in 09-0063 ofICDD, and the above powder forms a layer halite structure similar tothat of LiNiO═. Observation of the above powder was further carried outusing a scan-type electronic microscope, and results of the observationconfirmed particles having a configuration consisting of aggregation ofprimary grains of 0.1 μm to 41 μm.

Then, 86% of lithium-transition metal composite oxide B thus prepared,10% of graphite as a conductive material, and 4% of PVdF as a binderwere mixed and further dispersed into NMP to obtain a compound materialin a slurry form. The slurry-formed compound material was uniformlycoated on a long strip-shaped aluminum foil of 20 μm thick, dried,compressed using a roller press machine, and punched out in apredetermined size to thereby obtain a pellet. Thus-fabricated pelletwas used as a cathode, while a lithium foil was used as an anode, andthese electrodes were stacked while placing a known porous polyolefinfilm in between to manufacture a coin cell having a diameter of 20 mmand a height of 16 mm. For the electrolyte solution, a non-aqueouselectrolyte solution was prepared by dissolving LiPF₆ in a solutionobtained by mixing ethylene carbonate and methyl ethyl carbonate in avolume mixing ratio of 1:1 so as to adjust the concentration thereof to1 mol/dm³.

Thus-fabricated coin cell was charged up to 4.250 V, then dischargedunder a current of 0.2 C down to 3.000 V, and resulted in a meandischarge voltage of 3.827 V.

(3) Preparation of Cathode Active Material

Thus-prepared lithium-transition metal composite oxide A andthus-prepared lithium-transition metal composite oxide B were mixed sothat a molar ratio thereof becomes 90:10 to thereby prepare a cathodeactive material.

(4) Manufacture of Cylindrical Battery

86% of cathode active material described above, 10% of graphite as aconductive material and 4% of PVdF as a binder were mixed and furtherdispersed into NMP to obtain a cathode compound material in a slurryform. The slurry-formed compound material was uniformly coated on theopposite faces of a long strip-shaped aluminum foil of 2 μm thick,dried, and compressed using a roll press machine to thereby obtain along strip-shaped cathode.

Next, for an anode, to 90% of artificial graphite in a powdered form wasadded 10% of PVdF and further dispersed into NMP to obtain an anodecompound material in a slurry form. The slurry-formed anode compoundmaterial was uniformly coated on the opposite faces of a copper foil of10, μm thick, and compressed using a roll press machine to therebyobtain a long strip-shaped anode.

Thus-fabricated strip-shaped cathode and long strip-shaped anode werespirally wound up a large number of times while placing a porouspolyolefin film in between to fabricate a spirally wound electrodemember. Thus-fabricated electrode member was enclosed in a batterycontainer made of nickel-plated iron, and insulator plates were mountedto both upper and lower faces of the electrode member.

Next, a cathode lead made of aluminum was extracted from a cathodecurrent collector and welded to a projection part of a safety valvewhose electrical conduction to the battery cap has been ensured, and ananode lead made of nickel was extracted from an anode current collectorand welded to a bottom of the battery container.

Meanwhile, for the electrolyte solution, a non-aqueous electrolytesolution was prepared by dissolving LiPF₆ in a solution obtained bymixing ethylene carbonate and methyl ethyl carbonate in a volume mixingratio of 1:1 so as to adjust the concentration thereof to 1 mol/dm³.

Then, the above electrolyte solution was poured into the batterycontainer with the above electrode member incorporated therein, and thesafety valve, the PTC element and the battery cap were fixed by caulkingthe battery container while placing an insulator sealing gasket inbetween to thereby manufacture a non-aqueous electrolyte secondarybattery having a shape of cylinder with an outer diameter of 18 mm and aheight of 65 mm.

Example 45

LiNi_(0.35)Co_(0.25)Mn_(0.4)O₂ was prepared under conditions that amixing ratio of materials in Example 44 was altered in preparation ofthe lithium-transition metal composite oxide B, and measurement of amean discharge voltage was carried out similarly and resulted in 3.895V.

Then, thus-prepared lithium-transition metal composite oxide B and thelithium-transition metal composite oxide A prepared in Example 44 weremixed similarly to prepare a cathode active material, and thereafter,the non-aqueous electrolyte secondary battery in this Example wasmanufactured by repeating operations similar to those of Example 44.

Example 46

LiCo_(0.8)Ni_(0.2)O₂, was prepared under conditions that part of cobaltoxide as the material in Example 44 was substituted with nickelhydroxide in preparation of the lithium-transition metal composite oxideA, and measurement of a mean discharge voltage was carried out similarlyand resulted in 3.911 V.

Then, thus-prepared lithium-transition metal composite oxide A and thelithium-transition metal composite oxide B prepared in Example 44 weremixed similarly to prepare a cathode active material, and thenon-aqueous electrolyte secondary battery of this Example wasmanufactured by repeating operations similar to those of Example 44.

Comparative Example 15

The non-aqueous electrolyte secondary battery of this Example wasmanufactured by repeating operations similar to those of Example 44using a cathode active material composed of only the lithium-transitionmetal composite oxide A prepared in Example 44 without being added withthe lithium-transition metal composite oxide B.

Comparative Example 16

The non-aqueous electrolyte secondary battery of this Example wasmanufactured by repeating operations similar to those of Example 44using a cathode active material composed of only the lithium-transitionmetal composite oxide A prepared in Example 46 without being added withthe lithium-transition metal composite oxide B.

Comparative Example 17

LiCoO₂ and LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂ were prepared under conditionsthat a mixing ratio of materials in Example 44 was altered inpreparation of the lithium transition metal composite oxide B, andmeasurement of a mean discharge voltage was carried out similarly andresulted in 3.919 V.

Then, thus-prepared lithium-transition metal composite oxide B and thelithium-transition metal composite oxide A prepared in Example 44 weremixed similarly to prepare a cathode active material, and thenon-aqueous electrolyte secondary battery in this Example wasmanufactured by repeating operations similar to those of Example 44.

[Evaluation of Over-Discharge Resistance]

Thus-fabricated non-aqueous electrolyte secondary batteries in Examplesand Comparative Examples were subjected to measurement of initialdischarge capacity on condition that these batteries were charged undera voltage of 4.20 V and a current of 1000 mA in an atmosphere of 23° C.for 2.5 hours, and thereafter discharged under a current of 800 mA downto 2.75 V. Subsequently, constant resistance discharge was carried outfor 24 hours as an over-discharge test by connecting a resistance of 2.00 so as to be placed between the cathode and the anode. Then,measurement of discharge capacity after the over-discharge test wascarried out according to the similar procedure to that used formeasurement of the initial discharge capacity, so as to calculate acapacity retention ratio in proportion to the initial dischargecapacity. Table 6 shows the evaluation results.

TABLE 6 Over-discharge Cathode active material resistance Lithium- Meandischarge Capacity transition voltage (V) Initial after metalLithium-transition Mixing Difference discharge over- Capacity compositemetal composite ratio between capacity discharge retention oxide A oxideB A:B A B A and B (mAh) (mAh) ratio (%) Example 44 LiCoO₂LiNi_(0.6)Co_(0.2)Mn_(0.2)0₂ 90:10 3.948 3.827 0.121 1890 1780 94.2 45LiCoO₂ LiNi_(0.35)Co_(0.25)Mn_(0.4)0₂ 90:10 3.948 3.895 0.053 1880 173092 46 LiCo_(0.8)Ni_(0.2)0₂ LiNi_(0.6)Co_(0.2)Mn_(0.2)0₂ 90:10 3.9113.827 0.084 1900 1810 95.3 Comparative 15 LiCoO₂ None 100:0  3.948 —1860 1310 70.3 Example 16 LiCo_(0.8)Ni_(0.2)0₂ None 100:0  3.911 — 18901350 71.4 17 LiCoO₂ LiCo_(0.8)Ni_(0.1)Mn_(0.1)O₂ 90:10 3.948 3.919 0.0291880 1500 79.8

As judged from the above results, it was confirmed that adding thesecond lithium-transition metal composite oxide B to the firstlithium-transition metal composite oxide A results in improvement ofover-discharge characteristics. It was also proved that a smalldifference in mean discharge voltage between these composite oxides Aand B fails to obtain sufficient effects, while a difference in meandischarge potential as much as 0.05 V or more is successful in achievingsufficient effects.

Example 47

A cathode active material was prepared under conditions that thelithium-transition metal composite oxide A and the lithium transitionmetal composite oxide B prepared in Example 44 were mixed in a molarratio of 98:2, and then, the non-aqueous electrolyte secondary batteryin this Example was manufactured by repeating operations similar tothose of Example 44.

Example 48

A cathode active material was prepared under conditions that thelithium-transition metal composite oxide A and the lithium-transitionmetal composite oxide B prepared in Example 44 were mixed in a molarratio of 96:4, and then, the non-aqueous electrolyte secondary batteryof this Example was manufactured by repeating operations similar tothose of Example 44.

Example 49

A cathode active material was prepared under conditions that thelithium-transition metal composite oxide A and the lithium-transitionmetal composite oxide B prepared in Example 44 were mixed in a molarratio of 70:30, and then, the non-aqueous electrolyte secondary batteryin this Example was manufactured by repeating operations similar tothose of Example 44.

Example 50

A cathode active material was prepared under conditions that thelithium-transition metal composite oxide A and the lithium-transitionmetal composite oxide B prepared in Example 44 were mixed in a molarratio of 50:50, and then, the non-aqueous electrolyte secondary batteryin this Example was manufactured by repeating operations similar tothose of Example 44.

Example 51

A cathode active material was prepared under conditions that thelithium-transition metal composite oxide A and the lithium-transitionmetal composite oxide B prepared in Example 44 were mixed in a molarratio of 40:60, and then, the non-aqueous electrolyte secondary batteryin this Example was manufactured by repeating operations similar tothose of Example 44.

[Evaluation of Over-Discharge Characteristics]

Thus-fabricated non-aqueous electrolyte secondary batteries weresubjected to over-discharge test similar to the above. Table 7 showsevaluation results.

TABLE 7 Mixing ratio (molar ratio) of first lithium-transition metalcomposite Over-discharge oxide A resistance to second lithium- InitialCapacity Capacity transition metal discharge after over- retentioncomposite oxide B capacity discharge ratio A:B (mAh) (mAh) (%) Example47 98:2  1890 1480 78.3 48 96:4  1890 1750 92.6 49 70:30 1870 1770 94.750 50:50 1850 1790 96.8 51 40:60 1710 1660 97.1

As judged from the results summarized in Table 7, it was confirmed thata mixing ratio of the second lithium-transition metal composite oxide asmuch as less than 4% results in degradation of over-dischargecharacteristics, while a mixing ratio thereof as much as more than 50%is susceptible to degradation of initial discharge capacity. It was alsoconfirmed that a preferable mixing ratio of the secondlithium-transition metal composite oxide B is in a range of 4% or moreand 50% or less.

As has been described in the foregoing, according to the presentinvention, use of the cathode active material containing the mixture ofthe first cathode material having a large capacity and the secondcathode material exhibiting a stabled crystal structure achieves thenon-aqueous electrolyte secondary battery that is successful in raisinginitial discharge capacity and in increasing an energy density and hasexcellent charge/discharge cycle capacity retention ratio not only atroom temperature but also under high temperature environment.

According to the present invention, the lithium composite oxide, inwhich variation of nickel ion during charging/discharging when measuredusing X-ray absorption fine structure analysis (XAFS) falls in apredetermined range, is used, so that it is possible to provide thecathode active material that may realize a lithium ion non-aqueouselectrolyte secondary battery having a large capacity and largelyimproved characteristics under high temperature environment (in a rangefrom a room temperature to 100° C. or around) and also to provide thelithium ion non-aqueous electrolyte secondary battery using this cathodeactive material.

Furthermore, according to the present invention, the firstlithium-transition metal composite oxide mainly containing lithium andcobalt and the second lithium-transition metal composite oxide whosemean discharge voltage is lower than that of the above composite oxideby 0.05 V or more are contained, so that it is possible to provide thecathode active material that may realize the lithium ion non-aqueouselectrolyte secondary battery having a large capacity and beingexcellent in over-discharge resistance, and also to provide the lithiumion non-aqueous electrolyte secondary battery using this cathode activematerial.

1-8. (canceled)
 9. A cathode active material used for a lithium ionnon-aqueous electrolyte secondary battery comprising: a mixture of afirst cathode material containing at least Ni and Co and a layerstructure; and a second cathode material containing at least Ni and Mnand comprising a layer structure, wherein said cathode active materialcontains a lithium composite oxide having a layer structure, containingat least lithium and nickel as components, and in which a shift width of50% position of jump height of nickel-K shell absorption edge obtainableby measurement using X-ray absorption fine structure (XAFS) analysistechnology is equal to or more than 1.0 eV when 50% of the whole lithiumcontents was extracted.
 10. The cathode active material according toclaim 9, characterized in that said lithium composite oxide furthercontains manganese and/or titanium.
 11. The lithium ion non-aqueouselectrolyte secondary battery according to claim 9, characterized inthat, in a lithium ion non-aqueous electrolyte secondary battery havinga cathode and an anode respectively consisting of a cathode activematerial and an anode active material composed of materials capable ofinserting and extracting lithium ion; and a non-aqueous electrolytehaving lithium ion conductivity, said cathode active material iscomposed of a lithium composite oxide having a layer structure,containing at least lithium and nickel as components, and in which ashift width of 50% position of jump height of nickel-K shell absorptionedge obtainable by measurement using X-ray absorption fine structure(XAFS) analysis technology is equal to or more than 1.0 eV when 50% ofthe whole nickel contents is extracted.
 12. The lithium ion non-aqueouselectrolyte secondary battery according to claim 11, characterized inthat said lithium composite oxide contains manganese and/or titanium.13. The lithium ion non-aqueous electrolyte secondary battery accordingto claim 11, characterized in that an amount of nickel in said cathodeactive material is adjusted to a range from 5% to 40% in a molar ratio.14. The cathode active material used for the lithium ion non-aqueouselectrolyte secondary battery according to claim 9, characterized inthat said cathode active material is composed of a firstlithium-transition metal composite oxide mainly containing lithium andcobalt and having a layer structure, and a second lithium-transitionmetal composite oxide having a layer structure and whose mean dischargevoltage resulting from discharge under a current of 0.2 C down to arange of 4.25 V to 3.00 V is lower than that of said firstlithium-transition metal composite oxide by 0.05 V or more.
 15. Thecathode active material according to claim 14, characterized in thatsaid second lithium-transition metal composite oxide is contained in arange from 4% to 50% in molar ratio.
 16. The lithium ion non-aqueouselectrolyte secondary battery according to claim 14, characterized inthat, in a lithium ion non-aqueous electrolyte secondary battery havinga cathode and an anode respectively consisting of a cathode activematerial and an anode active material composed of materials capable ofinserting and extracting lithium ion; and a non-aqueous electrolytehaving lithium ion conductivity, said cathode active material iscomposed of a first lithium-transition metal composite oxide mainlycontaining lithium and cobalt and having a layer structure and a secondlithium-transition metal composite oxide having a layer structure andwhose mean discharge voltage resulting from discharge under a current of0.2 C down to a range of 4.25 V to 3.00 V is lower than that of saidfirst lithium-transition metal composite oxide by 0.05 V or more. 17.The lithium ion non-aqueous electrolyte secondary battery according toclaim 16, characterized in that said second lithium-transition metalcomposite oxide is contained in a range from 4% to 50% in molar ratio.